Chapter 2


The first section of this chapter describes how to set up your PX-8 for the first time. The remainder of the chapter deals with the general functions of the computer.

2.1 Starting Up

2.1.1 Precautions

a) The computer

The PX-8 is a precise machine and in order to achieve the best performance, you should observe the following points:

  1. Avoid using or leaving the PX-8 in a place exposed to direct sunlight.
  2. Avoid using or leaving the PX-8 in a damp place.
  3. Avoid using or leaving the PX-8 in a place exposed to strong vibration.
  4. Avoid using or leaving the PX-8 in a place exposed to high temperatures.
  5. Do not allow the PX-8 to be subjected to shocks of any kind.

b) The AC adapter

An AC adapter is provided with the PX-8 to re-charge the built-in batteries. When using this AC adapter:

  1. Avoid plugging the adapter plug into the AC adapter jack of the PX-8 without plugging the adapter to an AC outlet.
  2. The shape of the power plug differs according to the country for which the PX-8 has been shipped. In certain countries there may not be a power plug attached. Your dealer will be able to advise you on the correct plug in this case.
  3. The PX-8 will take approximately 8 hours to charge if the PX-8 is switched off. However, if the power switch is ON the time will be greater (at least 11 hours if no access is made to any device including the keyboard).

    page 2-1

  4. If you use the PX-8 while charging it at the same time, you will not be able to use it for as long as you might expect. If you intend to use the PX-8 from the battery alone, the adapter should be removed from the PX-8 and then reinserted in order to ensure it will fully charge. You should then en- sure that it is left for at least 8 hours before use in order to achieve the maximum length of use.
  5. The maximum length of use on battery power is 15 hours without In- put/Output operation.
  6. There are special circuits to prevent overcharging of the battery.
WARNING: Never use any AC adapter other than that provided.

2.1.2 Before switching on

Your PX-8 cannot be used immediately after unpacking. The following proce-dures must be carried out before turning on the power switch.

Your dealer will probably have carried out the procedures in this section when you receive the computer, in which case you can go to section 2.2 to see how to operate the computer, although you may find it helpful to continue reading. a) Inserting and charging the battery
The PX-8 has been designed as a portable computer powered by rechargeable internal batteries. There are two battery units, main and backup. When the main batteries have insufficient power to allow continuous operation, the LED lights at the top of the keyboard marked CAPS, NUM and INS will flash and the following message will appear on the screen for 20 seconds:


Then the power is automatically turned off and the backup battery takes over so that the program or work in progress is retained until the batteries can be re-charged. If the computer is not switched on the batteries are used to retain the contents of the memory. It is possible, therefore, for the batteries to be-come discharged. In order to prevent this the computer will normally be shipped with no main batteries. You should therefore proceed as follows:

  1. Insert the batteries as described in the addition sheet, or as described in Appendix C. page 2-2
  2. Plug the AC adaptor power cable into an AC outlet.
  3. Plug the AC adaptor output cable into the PX-8 adaptor jack.
  4. About 8 hours (or 11 hours if the power switch is left on) are required to fully charge the battery units.

If when you come to switch on the computer the "CHARGE BATTERY" mes-sage comes up on the screen, it is still possible to use the computer while it is charging.
IF NO DISPLAY IS VISIBLE WHEN YOU FIRST SWITCH ON THE COM-PUTER the batteries may be discharged. This can occur at any time. Simply plug in the charger, wait 10 seconds and then switch on again.

IF NO DISPLAY IS VISIBLE AT THIS STAGE, the batteries are so low that all the power is being used to charge them and there is no additional power available to perform the normal functions of the computer. Switch the power switch off, wait a few minutes and try again.

b) DIP switch settings
As mentioned in Chapter 1, all of the layouts of character keys shown in table 2.1 are available with your PX-8 regardless of the markings on the key tops. The keyboard layout can be altered by means of the DIP switch (SW 4) which lies under a cover beneath the PX-8 near the keyboard (see fig 2.2). It is also possible to alter the character set by means of software. This is described in Appendix A ‘ESC codes’ using ESC "C" and Chapter 3 under the CONFIG.

Open the DIP switch cover underneath the PX-8 (fig 1.le) and check that the DIP switch settings correspond to the characters for the country you require, page 2-3

as follows:

When you open the DIP switch cover you will see a silver flexible flap. Lift this out of the way and the DIP switch will be seen on the left (if the DIP switch cover is towards you as you are looking at the base of the PX-8). The DIP switch can then be set. The individual switch is in the ON position when it is towards the side which is marked ON.

Only the first four positions of the DIP switch are used for the character sets. The settings for various keyboard layouts are shown in table 2.1. The switches can be changed with the tip of a ball point pen or a matchstick.

Fig. 2.2

Table 2.1
DIP switch position


  1. IMPORTANT: Altering the settings will not cause any change to occur un- til the reset procedure outlined in section 2.2.5 is carried out.

    page 2-4

  2. Other DIP switch settings are used for different purposes. The position of switch 5 is used to decide whether a RAM check should be carried out if an Intelligent RAM disk is connected. Switch 6 is concerned with certain characters output to the printer when a screen dump is carried out. Both of these will be explained in Chapter 4.
  3. Switches 7 and 8 are not used. They should be left in the OFF position as set in the factory.

2.1.3 Initialization

There are a number of times when it is necessary to reset the system. There are three different ways of resetting the system. The action of these three reset modes are summarised in section 2.2.4.

A complete reset (resetting the sub-CPU) and initialization must be carried out if:

  1. The batteries have been changed or inserted for the first time on purchasing.
  2. The system has become so corrupt as to leave no alternative but to carry out a complete reset. This is a very rare occurrence and there are less dras- tic ways of resetting the computer. The complete reset procedure should only be attempted as a last resort. See section 2.2.4 for a comparison of the different reset situations.
  3. The optional expansion unit has been installed. (e.g. RAM Disk Unit)

a) Resetting the sub-CPU

The procedure for resetting the 7508 sub-CPU is as follows:

  1. Turn off the power switch.

    Fig. 2.3

    page 2-5

  2. Open the plastic switch cover on the base of the PX-8.

    Fig. 2.4

  3. Press the push button reset switch near the DIP switch. The switch is co- vered to present accidental resetting of the sub CPU. It has a hole in the top through which it is possible to push the switch. Do not use a conduc- tive implement to push the switch, or one whose end can break off (e.g, a pencil).

    Fig. 2.5

    page 2-6

  4. Replace the cover. Turn the PX-8 over and switch the power back on. The following message will then be displayed on the LCD screen:

    Fig. 2.6

After about 10 seconds the screen will clear and show the menu screen.

Fig. 2.7

This display image is the same as that displayed after system initialization described in Section 2.2.5.b.

2.1.4 The initialization process

During this initialization the PX-8 is set up ready for use. The initialization process simply assigns fixed values to the system parameters. If you find it neces-sary to carry out this initialization when you have been using the PX-8, then some settings will be changed. If you require full details of the parameters they are tabulated in section 2.2.4.d.

You can start to use the PX-8 straight away, although you may wish to set some of the parameters before continuing. They can be set using the utility program named CONFIG, the use of which is described in full in Chapter 3. The most important values you need to change are the time, and the RAM disk size.

The PX-8 has a built in clock. This has other functions besides telling you the time and date. It allows the PX-8 to be switched on and off under program control. This enables an alarm to be sounded and a message displayed at a time

page 2-7

you can set. It also enables you to set the PX-8 to switch itself on and execute a program at a chosen time. The clock can also be utilized by applications pro-grams. The program PORTABLE SCHEDULER&tm; enables a diary to be kept which automatically switches on the PX-8, or interrupts the program you are using, to remind you at the time and date you have set.

In order to make the PX-8 fully portable it needs to be able to store and retrieve data and programs easily without the need for other additional equipment. This is achieved in the PX-8 in a number of ways. There is a built in microcassette drive, but this is primarily intended for storing data. In order to achieve fast loading of programs, there are two ROM socket which function as if they were conventional CP/M disk drives. It is also possible to allocate part of the inter-nal memory to act as a RAM disk. A much greater capacity RAM disk can be added to the PX-8 to give up to 120 Kilobytes (KB) of storage. This is described in section 4.1.3. When the PX-8 goes through the initialization proce-dure, it sets the size of the internal RAM disk to 9 KB if an external RAM disk is not fitted. This can be changed to make the RAM disk use up to 24KB of memory.

If this reset sequence has to be carried out when the PX-8 has been in use, all files in the RAM disk will be lost. It is thus good practice to backup the RAM disk by transferring the files to tape as often as is con-venient. This also applies to the Intelligent RAM Disk unit if fitted. If you try to initialize with the Intelligent RAM Disk unit write protected, it will not be possible for the initialization to go to completion because it cannot initialize the disk. The message "initializing" will continue on the screen indefinitely. If this happens, switch the Intelligent RAM Disk write protection switch to OFF and the procedure will be completed.

The RAM disk size and the time and date can be reset using the CONFIG pro-gram on the utility ROM. Full details on how to use CONFIG are given in sec-tion 3.8.6. However, since you would normally set the time and date after initializing the PX-8, this is used as an illustration of operating the computer. First, however, it is necessary to understand the keyboard.

page 2-8

2.2 Operating the Computer

2.2.1 The keyboard

If you are used to using a normal typewriter or another computer, you will see that the keyboard is similar. You will already have used the keyboard if you have set up and initialized the PX-8, but in order to use all of its facilities you will need to study this section to understand the special keys and key combina-tions. There are also special key combinations which only apply if you are us-ing CP/M, the BASIC language or a particular applications program. Special use of certain keys and key combinations under CP/M are explained in Chap-ter 3, and under BASIC in the BASIC Reference Manual. Consult the appropri-ate Manual for any applications software.

a) Alphanumeric keys

Most keys on the keyboard generate characters, alphabetic, punctuation and numerals or graphics characters. These keys are called auto-repeat keys. Each auto-repeat key generates a certain character code repeatedly if it. is pressed and held on for more than a specified period of time. This normally causes a charac-ter to be printed on the screen. Some keys are switch keys which alter the charac-ter code output by the character keys, for example to allow one key to output either upper or lower case characters. Other keys are special keys which allow insertion and deletion of characters, for example.

Fig. 2.8

page 2-9

The time before starting repetition and the repetition interval can be set by the user by means of an ESC code sequence. See Appendix B.

If you are not familiar with a computer with auto repeat keys, you may hold them down too long initially, although you will soon adjust to the response time. If the key is held down past the repetition time, the character will be printed more than once and this could cause a program to respond in a way you might not expect.
Sometimes a key may not appear to respond. This is because a program is processing data. Do not press the key again as the key you have pressed is stored in a buffer and will be retrieved when the program is ready to use your input. Continued pressing of a key may cause action to occur which you did not intend.

b) Switch keys
Switch keys allow the other keys to perform more than one function. For example, they can allow upper and lower case (capital and small letters) to be obtained from the alphabet keys.

: Pressing this key together with a key other than a switch key enters the alternative code assigned to that key. The key should be held down before the other key is pressed. Thus if any numerical key is pressed whilst hold- ing the key down the alternative character above the numeral on that key will be printed. The key also allows upper and lower case letters to be obtained from the alphabetical keys.

: Pressing this key makes the alphabet keys enter upper case letters without pressing the key. The lock is removed by pressing the key again. When the is set the LED marked "CAPS" at the top of the key-board will be lit. If the key is pressed when the Caps Lock is set, the lower case character is printed instead.

: There are two ¿crRi keys, one to the left of the keyboard above the key, and one to the right of the space bar. They are equivalent. Pressing either key makes it possible to enter control codes from the keyboard. Control codes are characters which are not printed. Some correspond to charac-ters such as a carriage return, line feed, etc., others are used by applications software packages to perform such functions as clearing the screen or going to the end of the text. Control codes are normally associated with alphabetic keys and are indicated by the word "Control" followed by the associated let-ter, for example, "Control C". This is often abbreviated with the "CTRL"

page 2-10

joined to the letter by a hyphen. For example pressing the and the key at the same time could be written - . Another common way to show a control character is to place a ^ character in front of the letter. Thus - could also be written as ^C. This will be printed on the screen if a control character is entered on the command line in CP/M. To obtain a control character the key should be held down and then the alphabetic character pressed.

: This key has two functions. Pressing a character key together with this key enters the graphic character code assigned to the key. Not all keys have graphics characters assigned to them. It is also possible to have user defined characters. Those are defined in the codes indicated in ( ).

Fig. 2.9.a ASCII keyboard

If the key is pressed while the key is held down, a block of keys can be used as a numeric key pad. The key layout is as follows:

Fig. 2.9.b ASCII keyboard

page 2-11

When the PX-8 is in the numeric keypad mode the LED at the top of the key- board marked "NUM" will be lit. Pressing this key together with the key when the PX-8 is in this mode returns to the normal state.

c) Special keys There are a number of special keys some of which allow control of the cursor and also simplify operation of the PX-8. Some of them also allow interruption of the computer so that, for example, the screen can be dumped to a printer.

The CURSOR KEYS are the keys marked with arrows on the right of the key-board. They are used to move the cursor on the screen under control of the applications program. The cursor keys are not supported by CP/M.

: This means carriage return, and is normally used to place the cur-sor at the beginning of a line. Since this would place the cursor on top of the characters already printed, a line feed is normally added to a carriage return by the software. The key is also used to signal the end of entry when a sequence of characters are being entered into the computer, otherwise the soft-ware has no way of knowing when the user has finished. Until the carriage return character is entered, the software will wait for the next character, unless a sin-gle character entry is required. The ASCII code for a carriage return is 13 decimal (OD hexadecimal), which corresponds to a -

: In CP/M pressing this key clears the keyboard buffer and makes a warm start of the system. In BASIC it is used to stop a program.

and : Pressing these keys simultaneously immediately terminates I/0 operation, and makes a warm start of the system.

: Pressing this key enters an ESCAPE code (ASCII code 27 decimal). It is used frequently to exit from many of the special function programs of the PX-8.

: Pressing this key enters a PAUSE code (ASCII code 19 decimal) which can be used to stop printing to the screen. For example if there are too many files on a disk to be displayed on the screen at one time pressing the ¿vAusE key can temporarily stop the printing of the filenames. The effect of a pause can be reversed by pressing any other key.

and or : Pressing the and or I keys calls a subroutine specified.

page 2-12

: Pressing this key enters code (ASCII code 0). This is some-times used in applications software to show a table of commands etc. On the PX-8 the main use of the key is in combination with the key to enter the System Display.

and : Pressing these keys simultaneously turns on the System Display. This is described in full in section 2.2.4.a.

: This is a key which moves the cursor to pre-set positions across the screen. These are normally in steps of 8 characters. When the TAB key is pressed it generates an ASCII code 9.

: Pressing this key enters character (ASCII code 127 decimal). It is usually used to delete the character under the cursor. However, some ap-plication programs use it in different ways. It has a special use on the CP/M command line and this will be explained in Chapter 3.

: This is obtained by using the key with the key. Both keys must be pressed even if the key is active. It enters a - which has the ASCII code 12 decimal. If used in an applications program it normally clears the screen.

: Pressing this key enters an ASCII code 18 decimal. Normally this is used to allow characters to be inserted. Its use on the CP/M command line is described in Chapter 3, as it has a different function.

: This key is used to change the cursor tracking mode. The PX-8 dis-plays a window on a virtual screen. The cursor moves over the virtual screen. Normally the window follows the cursor. This is called tracking mode. The key (obtained by pressing the and key) is used to turn the track-ing mode on and off. If the key is pressed while the PX-8 is in tracking mode, the window will be frozen over a particular portion of the virtual screen. This is known as the non-tracking mode. Pressing the¿sCRN key when the PX-8 is in this mode will turn the tracking mode on again and move the window on the virtual screen so that the cursor is displayed in the window.

This key causes the cursor to Back-Space and delete the last charac-ter. It enters a BACKSPACE character (ASCII code 8). In some applications

software, and on the CP/M command line, it is the only way to delete a character.

page 2-13

: The key as the name suggests moves the cursor to the top left hand corner of the virtual screen (not the window).

KEYS TO : The Programmable Function keys

These are a set of keys which enable the user to enter a string of characters which will be printed when the key is pressed. This is as if they had been typed in by the user at the keyboard. The PX-8 is programmed with a default set of characters which allow the most common CP/M commands to be input with one keystroke. Also when BASIC is entered, a default set is available, which corresponds to the common BASIC commands.

The strings are altered by means of the CONFIG program in CP/M, which is described in Chapter 3. The BASIC Reference Manual describes how to alter them in BASIC.

Pressing a programmable function key together with the key enters a different user defined string. The names PF6 to PF10 are given to the shifted keys to , i.e. a value of 5 is added to the number of the program-mable function key if it is shifted.

Since there are ten function key strings it is sometimes difficult to remember which key has which string associated with it. The strings assigned to each func-tion key can be displayed on the eighth line of the screen. If the eighth line shows the following display:

Fig. 2.10

This means function key will print the characters "dir" when pressed, and "dump" when pressed with the shift held down (i.e. the key is pressed) and so on across the screen. The "" character means that the equivalent of pressing the key is also added to the characters printed. A is not added with the characters if it is likely that other commands or parameters need to be added.

page 2-14

The assignments can be changed using the CONFIG program described in Chap-ter 3. This also has an option to switch the display of these function key assign-ments on and off.

Pressing a programmable function key ( to ) together with the . key calls a subroutine specified by the user. If no subroutine is speci-fied, nothing happens.

Pressing the and keys simultaneously outputs the contents of the display screen to the printer.

2.2.2 Starting to use the computer - Using the MENU and set- ting the time and date

As will be seen in section 2.2.3, it is possible to switch the MENU off. After initializing the computer, the screen displayed is the MENU screen. This ena- bles easy selection of a program you wish to execute. This section uses the prac- tical problem of executing the CONFIG program as an example in the use of the computer, and an introduction to some of the terminology.

When you switch the PX-8 on, if it is in the default mode, or if you have in-itialized the computer, the MENU screen will be displayed. The following dia-gram shows the screen as it would be seen if the utility ROM is in socket 2 and the BASIC ROM in socket 1.

Fig. 2.11

The top line of the screen shows a message indicating that the screen displayed is the MENU screen, followed by the date, day and time. If you have initial-ized the computer, the date will consist of three pairs of zeros, the day will be Sunday, and the time will be a few minutes past midnight. These values exist after initialization, because the initialization sequence sets the date, day and time to zero. By the time the initialization is complete, the clock has been up-dated and the minutes and seconds are no longer zero. The rest of the line shows further information which is not important at the moment.

page 2-15

On the next line of the screen is the expression:


Note also that the third line of the screen also begins with C:PIP but that it is flashing together with the letters "COM" next to it. The flashing indicates which of the files on the MENU has been selected. By pressing the cursor keys, change the flashing expression. The left and right arrow keys allow movement along a line and the up and down keys selection of the position in a column. Note how the flashing expression is duplicated on the second line of the screen. The letters "COM" are not written on the second line of the screen, however. To understand why it is necessary to understand the meaning of the names on the MENU.

A full description of CP/M is given in Chapter 3. CP/M is the operating sys-tem of the PX-8, i.e. it controls the various functions of the computer so that you can use it. CP/M saves programs and data or other collections of informa-tion as a file. Files have two parts to their name, the first part is simply the name of the file, for example “PIP” or “CONFIG”. The second part of the name (often called the extension) is a description of the type of file (for exam-ple “COM”). The type of files with the extension “COM” are application pro-gram files or utility programs. In this example the utility program “CONFIG” will be executed.

Select the program by using the cursor keys so that “C:CONFIG - COM” is flashing and the second line of the screen shows the expression “C:CON-FIG”. Note that the extension is not duplicated on the second line. This is be-cause CP/M does not need the extension; indeed it will generate an error if you try to use it when trying to execute a COM type file.

The “C:” before the filename denotes the drive in which that file is located. On a more conventional CP/M computer, the drive refers to floppy disk drive. On the PX-8, the drives also include the part of memory allocated as a drive, the RAM disk, and the two ROM drives. The correspondance between the drives and their identifying letter is given in section 3.3.1. The ROM drives have the letters B and C and the RAM drive is drive A. In fig 2.11, the utility programs are on drive C: and the BASIC interpreter file is on drive B:

With the CONFIG utility program selected (C: CONFIG COM is flash-ing and C: CONFIG is on the command line of the MENU page – the second

page 2-16

line) press the key. The screen will clear and then show


for a few seconds before the screen clears to show the CONFIG menu.

Fig. 2.12

To change the date and time, chose option by pressing the key and enter the date as the month, day and year. For example to change the date to the eleventh of August 1985, type:


and press the RETURN key. You can then enter the time. For example to set the time to 15:05 type:


It is necessary to add a zero for the seconds, otherwise the time will not be ac-cepted. The time and date will be updated when you press the key. To exit from this item, press the key.

You can also change the size of the RAM disk by using the CONFIG program. Take option on the CONFIG menu. To change the size to 15KB, simply type in the characters "15" and press the key. Press the key to RETURN to the CONFIG menu and ESC again to return to the MENU screen.

A more extensive explanation of changing the time and date and the RAM disk size is given in section 3.8.6.

There is another way you can execute the CONFIG program. This is from the CP/M command line. If you are used to using a computer with CP/M as the operating system, it will be the way you have always executed programs. From the MENU screen, press the key. The screen will clear and show the

page 2-17

CP/M prompt. If you have initialized the system, it will show:


This shows that the default drive is drive A:, which means that it is not neces-sary to type a drive name before trying to access a file from that drive. However, if the CONFIG program is on drive C:, it is necessary to prefix the file name with the drive name. Although the MENU screen presents a system of execut-ing programs without typing the names, with certain utilities it is also possible to use the programmable function keys to save typing. Using CONFIG is one such case where this can be achieved, with programmable function key 5. However, it does not add the drive so type:


The PF key also adds the carriage return. When the PF5 key has been pressed, the file name CONFIG will be written to the screen automatically, and a few seconds later the CONFIG menu will appear. When you exit from CONFIG, you will be returned to the MENU screen.

2.2.3 Switching the PX-8 on and off

The PX-8 has a power switch on the right hand side (see fig 2.3) which is the normal way the computer is switched on and off at the beginning and end of a session of using the PX-8. However, the PX-8 is not switched off completely as a mains operated computer would be if the power was turned off. The pow-er switch can be thought of as a means of temporarily halting the operation of the computer, so that the batteries are conserved. As soon as the power is turned on again it is possible to begin exactly where you left off, even if you were in the middle of typing a word or running a program.

The power switch is not the only means by which the power can be switched on and off. The power switch of the PX-8 is controlled by the computer, and can be switched off under software control. Thus, if it is not used for a length of time (which can be set by the user using the CONFIG program described in Chapter 3), it will switch itself off to conserve power. The user can also pro-gram the computer to switch itself off at specific times. Furthermore the PX-8 can switch itself on, run a particular program and then switch itself on again to run the same or another program. This ability to switch itself on and off is a powerful feature of the computer.

page 2-18

To switch the power on when the switch is already in the on position, switch it off and on again. This means, holding the computer with the keyboard nearest to you, moving the switch towards you and then away from you again.

To switch the computer off when it is already in the off position, switch the power switch to the on position and then off again.

Because the computer can switch itself on and off, the power switch position may not reflect the true state of the power. For example if the PX-8 switches itself off, the power switch will still be in the on position, even though the pow-er is off. Similarly, if the PX-8 switches itself on, the power switch will be in the off position even though the power is on. Holding the PX-8 normally with the keyboard towards you, the power switch is on the right hand side of the computer. The ON position is towards the back of the computer. The OFF po-sition is towards the front of the computer.

There are also two ways to switch the power off: the restart and continue modes. The selected mode is determined by the conditions prevailing at the time the power is turned off. When the power is switched off in the restart mode, the Menu or CP/M command line display will be activated when the power is turned on again. When the power is switched off in the continue mode, the operation which is being executed when the power is turned off will be continued when the power is turned on again.

  1. Conditions under which the restart mode is selected:
  2. Conditions under which the continue mode is selected:

page 2-19


Any file in memory which has been partly written to an external disk will be fully written to the disk when the PX-8 is switched off in continue mode. *However, the cable should not be removed and the file should be closed in the normal way when switching on again. It is permissible to switch the disk drive off and on again whsle the PX-8 is switched off. If this procedure is not adhered to the file may be lost.

* The file will not be closed.


As can be seen from the above explanation, when the PX-8 is switched on, a number of routes can be taken by the operating system. If the power was switched off in the continue mode, operation will continue at the point at which it was switched off. If the PX-8 was simply switched off in the restart mode, there are a number of options possible. These also vary with the way the com-puter is switched on (i.e. manually or under the control of the PX-8). In order to understand these possible situations, an overview of the operating system is necessary. However, to keep the information together for reference, the fol-lowing summary of what can happen when the PX-8 is switched on is given at this point, even though some of the concepts have not been covered at this stage in the Manual.

  1. If the Password has been set the PX-8 will ask for the Password to be en- tered. It will not be possible to operate the system any further without en- tering the correct Password.
  2. If the PX-8 has been switched off in the continue mode, the program which was being used, will continue at the point it had reached when the PX-8 was switched off. Thus if the program was waiting for input, or was process- ing information, this would continue.
  3. If the PX-8 was switched off in the restart mode, either the MENU page or the CP/M command line would be displayed.
  4. If BASIC was in use when the PX-8 was switched off, it is possible to re- enter BASIC If the MENU is switched on, this is done simply by pressing the RETURN key. If the MENU is switched off, it would appear not to be present. It can be retrieved (see the SAVE command in Chapter 3), but you may not remember that you were using BASIC. It is wise to set the MENU on before switching off when using BASIC, so that it is evident that BASIC was in use, and to prevent any loss of programs stored in the five program areas.

page 2-20


First check that the view angle of the LCD is set so that you can see the screen display.

If there is still no display, the battery needs recharging. Plug in the AC charg-er, wait a few seconds and then switch on again.

2.2.4 The PX-8 operating system modules

The operating system of the PX-8 is functionally divided into several units which are referred to as modules. Some of them are part of the CP/M operating sys-tem and others supplement it.

  1. System Display module This module enables the microcassette tape to be operated manually and also to check and reset some of the system parameters. This module can normally be operated while applications software is running. Many of the following modules have parameters which can be changed by using this module.
  2. Password module This module makes it possible to stop unauthorised users from using the PX-8 without knowing an entry password.
  3. MENU module This module displays program files and data files on the screen and makes it easier for the user to run any program file by selecting it on the screen, using the cursor keys rather than having it to type the full name.
  4. Screen dump module This module is used to make a copy of the current screen on a printer.
  5. Console Command Processor (CCP) This is the part of the CP/M operating system which interprets command strings typed on the keyboard. This module includes the CP/M built-in commands (DIR, TYPE, REN, ERA, SAVE and USER).
  6. Basic Disk Operating System (BDOS) This is the part of the CP/M operating system which manages disk files. It also treats the ROM capsule and RAM as disk devices.
  7. Microcassette Tape Operating System (MTOS) This module manages microcassette tape files.
  8. Basic Input/Output System (BIOS) This part of CP/M which acts as the interface between the operating sys- tem and input/output devices e.g. the screen, keyboard and RS232 in- terface.

    page 2-21

  9. Microcassette Input/Output System (MIOS) I/0 interface between MTOS and microcassette firmware
  10. Clock module This module controls the alarm and wake functions and updates any time displays.
  11. System activator This module controls system activation, deactivation, the auto-start func- tion and initialization.

The best way to understand the operation of the modules which are directly under the control of the user is to check and alter the status of the parameters involved using the System Display module.

a) System Display module
The System Display is brought on to the screen by pressing the and key simultaneously. The screen is then changed to show a display similar to one of the following:

Fig. 2.13.a & b

This screen image is referred to as the System Display. It shows a number of items of information which would be hard to determine except by running a separate program to interrogate the system. Since the System Display can be' obtained even in the middle of an applications program it is a fundamental part of the PX-8 which you will be using regularly, so try altering as many of the parameters as possible to see what they do.

Looking around the screen you will see the following:

page 2-22

The first line shows the title "SYSTEM DISPLAY" in the top left hand corn-er. Followed by the date and time. It may show one or other of the words "<MENU>" and "<PASSWORD>". Figs 2.13 a and b show cases with and without these options displayed. These are visible if the corresponding op-tions have been set.

The second line shows the ALARM or WAKE time together with the appropri-ate string. If this option has not been specified, the line will be blank.

The third line shows the size of the RAM disk as set on initialization or using the CONFIG program (see Chapter 3). Next to it will be an Autostart string if one has been specified. The title " < AUTO START > " will still be present even if there is no string specified.

The fourth line shows the size of the USER BIOS, in 256 byte pages as set by initialization or the CONFIG program. To the right of the line are a series of parameters associated with the Microcassette drive.

The fifth line is concerned with the MENU. The drives from which the files will be taken are displayed next to the " < MENU DRIVE > " title on the left. The right hand side of the line shows which file extensions are to be chosen for display on the MENU.

The sixth line shows the prompt string and flashing prompt to enable one of the options on the seventh line to be taken.

unmounted, only the (shifted ) key will be active. The eighth line shows the strings associated with the programmable function

keys which are used to control the Microcassette drive. If a cassette has been

If the bottom line of the screen is blank, press the key to exit from the system display and execute a warm start by pressing the key or the and keys on the CP/M command line. Alternatively you can switch off and on again.

The following items CANNOT be changed by using the System Display:

1) Month/Day/Year (Day of week) (1st line)
2) Hour:Minute:Second (1st line)
3) RAM disk size (3rd line)
4) Size of USER BIOS area (4th line)

page 2-23

They are changed either by the initialization procedure, or the CONFIG pro-gram described in Chapter 3.

The following sections explore the use of each of the modules which can be changed by using the System Display.


System Display cannot be entered during PASSWORD or ALARM/WAKE display.

b) Password module

The Password module makes it possible to prevent the computer system from being used by unauthorised people. It should be used with care. It is not possi-ble for the Password to be determined once it has been assigned. If the Pass-word is being used, make sure that all data and programs including those in the RAM disk are saved to disk or Microcassette tape before switching off. If it is necessary to break the Password, all data and programs will be lost.

From the System Display press the key and lines 6 and 7 will change to:

Fig. 2.14

i) Setting a password

Fig. 2.15

with the cursor on the seventh line awaiting the password. Type in your pass-word (this is limited to 8 characters) and press the RETURN key when you have typed in all the characters. Remember the password you have typed because

page 2-24

there is no way to find out what it is once you have pressed RETURN

The System Display screen will show the word " < PASSWORD >" in the top right hand corner as soon as the RETURN key is pressed after the password has been entered.

Having entered a password, switch off the PX-8, wait a few seconds and switch it on again. The screen will now show:

Fig. 2.16

Fig. 2.16

The system cannot be used unless the correct password is typed from the key-board. Type the password and press the RETURN key. The letters you type will not be displayed on the screen. If the typed word is incorrect, the cursor will be returned to the starting position. When the correct word is entered, the speak-er will beep and the display will change to either the MENU page or the CP/M command line display.

ii) Removing the PASSWORD

Press the and keys to go back to the System Display again. This time after pressing 1, remove the password by pressing 1 again. If you had pressed 1 to change the password status and then decided not to do so, the mesc key could be used to return to the options choice line. In general, press-ing mesc anywhere in the System Display will successively take you back a level, so that you eventually leave it altogether.

The user will be asked to supply the password under the following conditions, not just when the PX-8 is switched on:

a) If power is turned on by the power switch or the wake time is reached with the password mode specified.

b) If the alarm or wake mode is activated while the password is still being en- tered, both will be treated as an alarm string.

page 2-25

The PX-8 will only treat the wake string as if it were an alarm string if the Pass- word is activated. The user will then be asked for the password again after press- ing to exit from the alarm/wake message.

c) Pressing the reset button will return the user to the password screen. The password mode is terminated in one of the following cases:

a) When the password is typed correctly. b) When power is turned off.

c) When the auto shut-off time is reached. d) When power failure is detected.

The password mode is interrupted when the alarm/wake time is reached.

The only way to exit from the password if it is not known is to initialize the system by either pressing the reset button with the right-hand and keys held down or by doing a full system reset, as when start-ing the up the system for the first time.

In this case all your programs will be lost and also anything stored in the RAM disk area.

page 2-26

c) Clock module - the ALARM and WAKE functions

The clock module manages the software clock and controls the ALARM and WAKE functions which allow the PX-8 to switch on and present a message or start a program running. If the computer is in use, and alarm or wake time is reached, the program being run will be interrupted. The screen will clear and show the message.

In order to familiarise yourself with the possible ways of setting and using the ALARM and WAKE functions press and to turn on the System Display and then press option 2 to change the ALARM and WAKE options. Lines 6 and 7 of the screen then change to:

Fig. 2.17

It is not possible to have both the ALARM and WAKE functions operating together. If option 2 is taken it will cancel any WAKE setting and replace it with an ALARM. Option 1 switches off whichever of the ALARM and WAKE has been set, and the message string (option 4) is used with both the ALARM and WAKE functions in a slightly different way.

i) Setting the ALARM

Before looking at the various options for setting the ALARM, the following example shows how to set the ALARM simply to switch on the computer and display a message at a specific time and date.

Press the key and the prompt changes as follows.

Fig. 2.18

page 2-27

The cursor is to the right of the prompt string. The PX-8 now expects you to type in the time at which you wish the alarm to sound. The prompt shows the order in which the date and time should be entered:

M: Month
D: Day
h: Hour
m: Minute

Care should be taken to ensure that a leading zero is added to a single digit value.

In order to have the alarm sound within a reasonable time, so that more exam-ples can be tried, set the date to that shown on the top line of the System Dis-play, and the time to two minutes later. As an example if the date and time shows "01/18/84 (WED) 11:38:45" enter "01181140" for the ALARM time. This ensures that the alarm will sound at "11:40" on the same day. When you reach the last character, the cursor will flash over this character, to show you that you are in the last position; otherwise the cursor will move to the next po-sition. If you decide you do not want to enter a value, simply press the I Esc I key. If one or more of the characters are wrong, you can move back and forth along the line using the cursor keys. When you press the key, the ALARM time will be entered onto the second line of the System Display.

The label "< ALARM MSG >" will appear to the right of the alarm time, but the rest of the line will be blank until a message string is inserted. As you have been returned to the prompt line shown in fig 2.17, press the key so that a message string can be inserted. Write a message of up to 40 characters, for example "Time to telephone home". When the key is pressed the mes-sage string will be entered next to the "< ALARM MSG > label.

When the alarm time is reached the speaker will sound a warbling note and the screen will clear to show the display of fig 2.19.

< Fig. 2.19

page 2-28

If no message string was entered, the rest of the line after the "< ALARM MSG >" label will be blank.

You can return to whatever was happening when the alarm sounded by press-ing the key. The alarm might also have occurred when the PX-8 was switched off. In this case the speaker would sound in exactly the same way and the power switched on to display the same screen. As this can happen when you might not be near the computer and the battery could be discharged, the computer will be automatically switched off after 50 seconds.

The PX-8 will exit from the ALARM screen when:

Unless the power is switched off the PX-8 will revert to the state it was jn im-mediately before the alarm was sounded.

ii) Ways of setting the ALARM

The example above showed how to set the alarm to go off at a specific time on a specific day. There are a number of ways that the alarm can be set, for example to repeat at specific intervals. This involves the use of wildcards. When an ALARM date and time is input, the PX-8 compares the current date and time with the string of characters input character by character. By using an aster-isk or question mark as a wildcard in the ALARM string, the comparison will regard the position where the wildcard character was inserted as always match-ing. For example, type " * * * * 0930" into the string following the "MMDDhhmm" prompt when taking the ALARM option. This will change the alarm time following the " < ALARM TIME >" label to " * * / * * 09:30". It will cause the alarm to sound every day at 9.30 am. The wildcard option is not completely flexible. It can only set the alarm to go off at intervals of one minute, ten minutes, one hour, twenty four hours and monthly. It is also pos-sible to set the ALARM to go off at specific intervals in a given period e.g. every ten minutes for an hour. The following table is a summary of how to use the wildcard.

page 2-29


Only the asterisk or question mark should be used as a wildcard character.

The time should be checked before exiting from the System Display as the PX-8 carries out a comparison between your string and the string output by the clock. If the alarm does not go off when you expect it to, check the System Display to see that the time you entered was correct.

iii) Setting the WAKE function

The wake function makes it possible to automatically turn on the power and/or start a program or execute a command at any desired time.

Note that the WAKE or ALARM cannot be used together.

The procedure for setting the WAKE time is the same as that for setting the ALARM time, except that option 3 is taken instead of option 2 (Fig 2.17). All the wildcard options can be used in the same way.

page 2-30

The message string (option 4 Fig 2.17) is used to name a program which is to be run. It is used in a similar way to the AUTO START string (see the next module). The string input into the WAKE message is used as if the characters were typed from the keyboard when the WAKE function switches the PX-8 on. Thus the message "A:PROGR^M" will run the CP/M COM file "PROG" on drive A: when WAKE switches the PX-8 on. The two characters at the end are a CTRL-M written as "^M". This is the carriage return character. Just as nothing will happen if you do not press the RETURN key when typing in a file name, so missing the "^M" from the end of a file name in a message string will normally cause the PX-8 to wait until the auto power off time is reached and then switch off.

For the options and rules to be followed in setting up a WAKE string, see the next module (the AUTO START string). Note that the WAKE string is entered as a message under the ALARM/WAKE option and NOT under the AUTO START string. The AUTO START string does not operate if the WAKE is ex-ecuted.

When you try out the WAKE function, remember that it won’t work unless you switch off the PX-8 before the WAKE time is reached. Set a WAKE time for a couple of minutes ahead and then enter a WAKE string. As an example you could use "DIR^M" to display a directory of the current drive. When the PX-8 switches on at the specified time, the MENU is ignored and the directory of the current drive will be displayed on the screen.

IMPORTANT: In adding the "^M" to the end of the message string in WAKE, the "M" must be upper case. If the message string following the "< WAKE STRG >" label has a "-" character at the end you have entered "m" and not "^M".

The action taken when the WAKE time is reached differs according to the state of the PX-8 when the wake time is reached.

The WAKE behaves as if it were an ALARM. This is to prevent the program initiated by the WAKE string from interrupting the task in hand when the WAKE time is reached. The speaker warbles and the display changes in the same way as if an alarm was sounded. Instead of the. WAKE string being a command string it is simply printed as a message string. The screen shows that a WAKE time (and not an ALARM time) has been reached when it appears as shown in Fig. 2.20, for example.

page 2-31

Fig. 2.20

The appropriate action can be taken, treating the WAKE as an alarm message. The same criteria apply for termination as apply to the ALARM time being reached.

The action taken will depend on the state of the PX-8 when switched off.

The power will be turned on and the program which was interrupted by switch-ing off wilt be continued. There will be no message, the computer will simply behave as if it had been turned on manually. ANY WAKE STRING WILL BE IGNORED.

  1. The power will be turned on and the WAKE string executed as if it had been typed in at the keyboard.
  2. If no WAKE string is specified the situation will be equivalent to the power being switched on manually, except that it will have been switched on auto- matically. Although the speaker will sound, there may not be anyone near the computer to notice that this has occurred. The PX-8 will then switch itself off when the auto-power-off time is reached.
  3. If no WAKE string is specified but an AUTO START string has been en- tered, the AUTO START string WILL BE IGNORED.
iv) AUTO START string

The AUTO START string is used to set a string which will be entered as if it had been typed from the keyboard when the PX-8 is switched on.

The AUTO START string will be ignored if the PX-8 is switched on in the con-tinue mode. When the computer has been switched off in the continue mode, this is because the computer has been stopped in the middle of a program exe-cution. To start up again with a new program could destroy valuable data.

page 2-32

To set the AUTO START string, press the key when the System Display is as shown in Fig. 2.13a or b.

The prompt changes as follows.

Fig. 2.21

To assign the string, press the key and the prompt changes as follows:

Fig. 2.22

As an example of how to use the AUTO START string from the System Dis-play type to select the AUTO START option.

When lines 6 and 7 show the options as in Fig 2.21 take option 2 and then type in the following string: "B:BASIC^M". This assumes the BASIC interpreter ROM is in the socket assigned to drive B: and should be changed to "C:BAS-IC^M" if it is in the C: drive socket.

Press the key when the string has been correctly entered.

Switch the PX-8 off in restart mode, i.e. simply switch off WITHOUT holding down the key.

Wait a few seconds then switch it on again. The screen will clear and place you on the CP/M command line and the characters "B:BASIC" will be printed next to the system prompt. Since the carriage return has been added by the PX-8 from the "^M" characters at the end of the AUTO START string, this will then be executed and about ten seconds later the BASIC program menu will be dis-played.

page 2-33

To cancel the auto start string, press the 1 key when the display is as shown in Fig. 2.21, and the display will change as shown in Fig. 2.13b.

To change the AUTO START string, carry out the procedure for assigning a string. The previous string will be displayed and can be edited. It is possible to delete the character to the left of the cursor but not to insert characters. Typing over a character replaces it. In many cases it is simpler to cancel the string and then reassign another one.

v) Rules for setting up AUTO START and WAKE Strings

1) If no carriage return is entered at the end of a string meant to be executed, the PX-8 will wait for the next character to be typed manually when switched on. This is the case either when the string is a WAKE string or an AUTO START string. A carriage return should be entered as the pair of characters "^M" and not as a lower case "^m". If the characters have been entered as "^m", the string will show "-" instead of the correct "^M".

If the carriage return is not present, the PX-8 will wait until the auto-power-off time is reached and then switch off.

2) If the WAKE string switches on the PX-8 the AUTO START string will be ignored even if the WAKE string is blank.

3) If the PX-8 is restarted, either manually or by the WAKE function, and the computer is in the continue mode the WAKE or AUTO START strings will be ignored.

4) If the PASSWORD is set the PX-8 will not be able to AUTO START or use the WAKE string until the password has been correctly entered.

5) The MENU is not used when the AUTOSTART or WAKE string is invoked on power up. This means that if BASIC is already resident, it is not possible to start up a BASIC program by loading it directly, or to run a program already in one of the program areas. However, it is possible to use a trick to overcome this problem. First go to the CP/M command line and type


This saves a special file onto the RAM disk. Details are given under the SAVE command.

page 2-34

of the BASIC program areas, the program "GO" can be used instead of the BASIC interpreter program. For example to run a program in area 4, use the following string for the AUTOSTART or WAKE string:

A:GO /R:4^M

To run the program START.BAS in the first program area, use the string:


To run the program START.BAS in program area 3, use the string:


This method must also be used with the ALARM and AUTOSTART com-mands in BASIC.

6) Control Codes 00H to 1FH can be set using the combination of "A" and ASCII codes (40H to 5FH).


If BASIC is resident and the A UTOSTART or WAKE string is not a BAS-IC program name (or even requests BASIC to be loaded), an error will be generated. Thus in setting up WAKE and AUTOSTART strings, note should be taken of the way the system is set up. It is best to set the system up specially for the AUTOSTART or WAKE, so that errors do not occur.

page 2-35

d) MENU module

When switching on the PX-8 it is sometimes difficult to find a particular pro-gram among a number of others on a disk device. Many of them may not be relevant. In many cases the same program is used over and over again, and like using the PF keys it is easier to press one key to load the program. The MENU module simplifies the selection of a program by allowing the types of file names which are displayed to be limited, and allows programs from a mix-ture of drives to be displayed together. It also allows the programs to be select-ed by movement around the displayed files using the cursor keys, and then running the program simply by pressing the key.

The MENU is controlled by option 4 of the System Display. Press the and key to turn on the System Display. Now press the key and lines 6 and 7 change to:

Fig. 2.23

Press the key and note how the label "<MENU>" comes up on the top right of the screen on the first line. It can be switched off using option 1 at this level. Before actually displaying the MENU, it is necessary to select which drives the files are to be chosen from and also which types of files are to be chosen from those drives. Chapter 3 explains the types of files. As a first illus-tration of the use of the MENU, choose option 3 and type "BC" and press the RETURN key. Note that these letters appear after the label "<MENU DRIVE > on the left of the fifth line and mean that files will be chosen from the B: and C: drives, i.e. the ROM drives In order to select a type of file, take option 4 and type "COM" and press the RETURN key. Note how the fifth line has changed so that the first file name extension (next to the label "< MENU FILE>" has changed to "COM".

When the PX-8 is initialized, the default drives are set to "ICBA". The I drive is a special ROM drive found only on versions of the PX-8 for the USA mar-ket. If this drive is not fitted, no action will be taken. Now press the key and the System Display returns to the first state. The MENU mode is set and the MENU screen will be displayed when the power switch is next turned on, or a warm start is made.

page 2-36

Turn off the power switch and then turn it on again. The speaker beeps and the following screen is displayed:

Fig. 2.24

The MENU screen is divided into three sections as shown below.

Fig. 2.25

Header section

The header section consists of the title "* * * MENU screen * * * ", date, day of the week, time, CP/M comment including the operating system version, current menu page and number of menu pages. If the number of files’ exceeds 120, "*" will be displayed at the end of the header section.

Command line

The command line section displays the currently selected file name, adding any COM file name if the file selected requires a COM file for execution. The Sys-tem Display is used to decide exactly what is printed on this line for each file, and the method of setting it is explained in the next few pages.

File name area

The lower part of the screen shows all the file names set up on the System Dis-play, chosen from the selected drives and the selected file extensions.

i) Using the MENU

The command line duplicates the name of the file in the top left of the file area and, to highlight the selected file, the name in the file area flashes. It is possible to change the selected file by using the cursor keys. Pressing the right arrow key moves to the right along a row, and then from left to right on the next

page 2-37

line. When the last filename is reached, the first one of the next line is selected to be displayed on the command line. The left arrow moves to the left in the same way. The up and down cursor keys allow movement in a column, but do not move into another column.

When a file name is on the command line, simply pressing the key will run that particular program. As an example, move the cursor keys until the file STAT is on the command line. As will be seen in Chapter 3, STAT is a program which gives STATistical information about the status of the com-puter and the disk drives. When STAT.COM (with its appropriate drive name prefix) is flashing, note that the drive name followed by STAT is printed on the command line. Press the key. The screen clears and the STAT program shows information such as the following:

Fig. 2.26

The second line of the screen shows the CP/M prompt and then the command line as would have been typed in had the STAT program been run directly from CP/M. This display shows a situation with the CP/M utilities in drive C: and thus the drive name C: would be displayed before the filename. After a few seconds, when the program has collected the information, the other lines are displayed. These show the space left on the various drives and whether they can be written to (R/W) or are read only (R/0). The CP/M prompt "A>" is then followed by the cursor.

In this case ending the program has returned the user to the CP/M command line. Sometimes when a program ends it will return to the MENU. If the STAT program had returned you to the MENU, all the information would have been erased from the screen before it could have been read.

Return to the MENU by using either the key or - and again place the STAT program on the command line. When the selected file has been placed on the command line, the cursor is placed to the right of the file name and is seen as a flashing underline character. This allows further parameters to be added from the keyboard. As an example of this use of the MENU, with

page 2-38

the STAT program on the command line, type in DEV: and then press the key. As is explained in Chapter 3, this shows the physical devices as-signed to the four logical devices. As before the screen will clear and show the command as if it were typed in from the CP/M command line, before display-ing the information a few seconds later. A possible display is shown in fig 2.27 below.

Fig. 2.27

ii) Setting the file extensions on the System Display

In setting the file extensions on the System Display care has to be taken in set-ting up files which are to be run as subsidiary files of a main COM file. The most common case of this is the use of BASIC files with the extension ".BAS". Other examples of extensions to filenames which denote subsidiary files are ".OVR" and ".DAT". Attempting to run these files without the appropriate COM file will result in an error. As an example of setting up the MENU to run subsidiary files, the following procedure should be used to set up BASIC files.

Enter the System Display and choose option 4, the MENU option.

Now edit the second extension by choosing option 5.

To specify the subsidiary file type its extension (for BASIC files the extension is ".BAS") followed by the filename of the COW file of which it is a subsidi-ary file. This is the reverse of normal CP/M conventions, but is necessary to display the extension correctly on line 5 of the System Display. Lines 6 and 7 would thus display:

page 2-39

Fig. 2.28

When the RETURN key is pressed, the right hand side of the fifth line will show

<MENU FILE> 1 .COM 2 .BAS 3 . 4.

However, if a file name is chosen with the extension ".BAS", for example "a:ZZZZ.BAS" the command line will show

b:basie a:ZZZZ.BAS

and when the RETURN key is pressed, BASIC will be loaded first and then the subsidiary file run.

If the MENU is used to run a program this way, since the BASIC inter-preter is loaded as well, any programs which are in the five program areas will be lost. A way to overcome this is described in the following section.

iii) Using BASIC from the MENU

Details of using BASIC on the PX-8 are given in the BASIC Reference Manu-al. When BASIC has been loaded and the PX-8 is switched off the first file from the disk drives will not be flashing. Instead the file area will show "BASIC (resident)" in the top left corner which will be flashing, and the command line will be blank. Simply pressing RETURN at this stage will cause the BASIC Pro-gram Menu to be turned on. Any programs in the five program areas can be run as described in the BASIC Reference Manual.

If BASIC is resident, the above method of selecting a BASIC program from the MENU will load the BASIC interpreter and destroy the programs in the five BASIC program areas. The following method will allow a BASIC program to be selected from the MENU and run while BASIC is resident.

i) Use either the MENU or the CP/M command line to load BASIC.

page 2-40

ii) Login to one of the program areas and type "system" or use PF8 (shifted PF3) to return to the CP/M command line or the MENU:.

iii) Either on the MENU or CP/M command line type:


The reason for doing this is explained in Chapter 3 under the SAVE command. iv) Enter the System Display and using option 5 on the MENU, alter the ex- tension to read:


This uses the COM file "GO" as the main file, with the BAS file as the subsidi-ary file.

When a file with the "BAS" extension is chosen from the MENU, if AND ONLY if BASIC IS RESIDENT, the MENU command line will show:


when the file "A:ZZZZ.BAS" is chosen from the menu, and the program will run directly in BASIC in program area one.

This method must also be used if BASIC is resident and the WAKE or AU-TOSTART string is used, and you do not wish to reload BASIC. Details are given in the previous section in the rules on using AUTOSTART and WAKE strings.

The MENU module is activated under one of the following conditions:

1) The MENU mode is specified and the AUTO START string is not specified in the System Display, and power is turned on by the power switch or when the wake time is reached.

2) The or and keys are pressed together when an appli-cation program which has been entered from the menu mode is being executed or the "SYSTEM" statement is executed in the BASIC mode.

page 2-41

Operation of the MENU module is interrupted in one of the following cases.

1) When the alarm or wake time is reached.

2) When the and keys are pressed together. (The system module is activated.)

3) When the and keys are pressed together. (The screen dump module is activated.)

The MENU module is started at the state at which it was interrupted when the MENU mode is returned to from one of the above conditions.

The MENU mode is terminated in one of the following cases:

1) When an application program is selected and the key is pressed.

2) When the AUTO POWER OFF time is reached.

3) When power failure is detected.

4) When the power switch is turned off.

5) When the key is pressed. (The screen clears and the CP/M system prompt appears on the screen.)

The MENU is ignored when the computer is switched on and one of the fol-lowing conditions prevail:

1) An AUTOSTART string has been specified.

2) A WAKE string has been specified and the PX-8 is switched on auto-matically.

The MENU will appear blank.

1) If no files of the specified type are present on the drives specified.

2) If the USER command is set and there are no files of the specified type.

page 2-42

e) Microcassette mode

The System Display is used to operate the Microcassette drive manually and also to check on the Microcassette mode settings. Full information on the Microcassette drive is given in Chapter 4.

i) Setting the Microcassette mode

To specify the Microcassette mode, choose option 5 on the System Display by pressing the 5 key.

Lines 6 and 7 of the screen then change to:

Fig. 2.29

Fig. 2.29

The stop and nonverify modes are automatically set after system initialization. Pressing the key sets the stop mode, pressing the, key sets the nonstop mode, pressing the key sets the verify mode and pressing the key sets the nonverify mode. Full details of the significance of these terms are described in Chapter 4 where the operation of the Microcassette drive is covered in depth.

The current settings for the Microcassette operation are shown on the right of the fourth line of the System Display, following the label "< MCT MODE >". This line also shows the position of the tape counter, following the "< COUNT >" label.

To return to the screen shown in Fig. 2.13.b, press the key. ii) Manual operation of Microcassette drive

The System Display is also used to allow the Programmable Function keys to operate the Microcassette drive manually. The function assigned to each of these keys is indicated on the 8th line of the system display shown in Fig. 2.13.b.

Two of the keys are assigned for fast winding of the tape forward and back-wards. These are the and keys which wind the tape on (< < - ) and rewind the tape ( - > >) respectively.

The urn key is used to play the tape at normal speed through the speaker.

page 2-43

The (shifted ) key is used to mount a tape, i.e. make it ready to be read from or written to by reading the directory into memory. When the tape is used first, the (shifted ) key can be used to initialize the tape by storing space for a directory. It is equivalent to formatting a conventional disk. The (shifted ) key is used to erase data from a tape. It does this from the current position of the tape.

The key is used to reset the tape counter to zero. The current position of the counter can be seen on the right of line 5 of the System Display next to the "< COUNT >" label.

The key marked with a character is the key to stop the cassette.

TO STOP THE MICROCASSETTE IN AN EMERGENCY press the and keys together.

If a Microcassette has been mounted, the only key which is assigned is ¿vve (shifted ). This will show the string "remove" which will allow the tape to be removed from the cassette drive. It is worth getting into the habit of check-ing the status of the cassette tape in the Microcassette drive, by inspecting the System Display BEFORE removing a tape from the drive. If a tape has been mounted, the eighth line will only show the word remove.

If a tape has been mounted, when the (shifted ) key is pressed, the screen will clear and show the message "remove" in the top left hand corner of the screen. If the tape has simply been read this will flash up momentarily, and the System Display will be redisplayed but with the eighth line showing the assignments for an unmounted tape.

If the tape has been written to, the revised directory on the tape will have to be written back on to the tape from memory. The tape will thus wind back to the beginning, and then record the updated directory. When this has been carried out, the System Display will be redisplayed but with the eighth line show-ing the assignments for an unmounted tape.


Do not change a tape and attempt to write to another one, without first removing the first tape and mounting the new one. Failure to observe this will almost certainly mean that data on both tapes will not be able to be read, and may also remove valuable data from the second unmounted tape.

page 2-44

f) The screen dump module

The screen dump module outputs the contents of display screen to a printer. It is activated by pressing the key together with the key or calling the BIOS SCRNDUMP routine in CP/M mode. In screen modes 0,1 and 2 data is sent to the printer in ASCII format, and in screen mode 3 in bit image format.

Printing stops when the and keys are pressed simultaneously, the power switch is turned off or power failure is detected.

If the printer is not ready, the module waits until it becomes ready.


If there is no printer attached to the PX-8, this creates a lock-up of the sytem. If this happens, press and keys together. No data will be lost if this happens.

page 2-45

2.2.5 Alternative reset sequences

Situations occasionally arise where the PX-8 ceases to respond to any instruc-tions from the keyboard when you expect it would. Even the key does not appear to work. The computer is said to be "hanging". This should not be confused with the situation where a program is processing data and takes seconds or even a minute to reach a situation where the user can input data again. When the system appears to have hung, it is sometimes possible to gain control by switching off, waiting a few seconds and switching on again. However, in most cases it is necessary to RESET the computer. There are a number of methods of resetting, which affect the system parameters to a differ-ent extent.


This is the most drastic reset procedure and is carried out as described in sec-tion 2.1.3. It must be carried out if the battery is changed, or if all other reset methods fail.

b) INITIALIZATION RESET This reset sequence is achieved by holding down the right-hand and keys while pressing the reset switch on the left of the PX-8 using the tip of a ball point pen or other similar implement. See fig. 1.1.c for the position of the reset switch.

This method of resetting, is for practical purposes as drastic as the sub-cpu reset and will cause loss of the current program, data and possibly destroy the RAM disk.

When this reset method is used, the initialization procedure outlined in section 2.1.3 will be carried out, and all data in the RAM disk will be lost.


Since all files in the RAM disk will be lost if either the SUB-CPU or the Initialization Reset sequences have been carried out, it is good prac-tice to backup the RAM disk files by saving them to the Microcassette drive as often as possible.


The least drastic method of resetting the PX-8 is to simply press the reset switch on the side of the computer using the tip of a ball point pen etc. In most cases very little harm will have been done to data, and most if not all variables in a program will probably still be intact. A number of system parameters will be changed and details of these are shown in table 2.3.

This method of resetting should be tried first.

page 2-46


In resetting the computer it is as well to be aware of the parameters which are altered by the reset action. The following table shows which settings are altered. Since these are normally the default settings of the system, these are shown also.

Table 2.3
ALARM/WAKE off - d d s,b
AUTO POWER OFF 10 mins - d d c,d
AUTO START off - d d s,b
CHARACTER SET DIP switch setting d d d  
CURSOR TYPE flashing block d d d c,b
DATE/TIME NOTE 1 - d d c,b
PF KEY DISPLAY off d d d c,b
I/O BYTE (03H) 10101001B d d d NOTE 9
MENU on - d d s
PASSWORD off remains d d s
PRINTER RS232C d d d c
RAM DISK SIZE 9K - d d c
RS232C NOTE 5 d d d c
SCREEN MODE mode 0 d d d c,b
USER BIOS SIZE 0 pages - d d c
  E2 - FE
del, cr symbols
WINDOW tracking mode d d d s,c,b

KEY TO abbreviations: d = default mode u = set by user on reset s = System Display c = CONFIG program b = BASIC

e Some functions can also be changed using ESCAPE code sequences as described in Appendix A.

page 2-47

The DATE and time are set to the default 00/00/00 00:00:00 with the day as zero (Sunday), and the user is asked to change them on reset.

The disk assignments for the default mode are shown in the explanation of the CONFIG program in Chapter 3.

The default Programmable Function strings are shown in the explanation of the CONFIG program in Chapter 3, and in section 2.2.1 above.

The default setting of the keyboard has the auto repeat start time set at 650 ms and the repeat interval at 75 ms. The keyboard is normal, in that all CAPS LOCKS etc are switched off. Any jumps to user functions using the keys and the , and ) to keys are set to a return.

The default RS232C settings are shown under the CONFIG program of Chap-ter 3.

The default setting of the Serial Interface are given in the explanation of the use of the CONFIG program in Chapter 3.

The User Defined Characters ASCII codes 224 to 254 (hexadecimal EO to FE) can be set using control code sequences as described in Appendix A. They can also be set from BASIC, and a program to do this is shown in Appendix H of the BASIC Reference Manual.

The first two characters 224 and 225 (EOH and E1H) have the default symbols for delete "" and a carriage return assigned to them. These characters are also frequently reset to the defaults at other times for example on power up. The character defined into ASCII code 226 (E2H) may also be corrupted on a reset.

The current drive is set by the applications program or from the CP/M com-mand line.

The use of the I/0 byte is described in Chapters 3 and 5.

page 2-48

NOTE 10:
Although the default drives for the MENU are set to "ICBA", if drive I: is not present, the MENU will only show the appropriate files on the other drives.

Priority of system reset

When a lock-up of the system occurs, reset the sytem according to the follow-ing priority.

  1. Press key.
  2. Press - keys.
  3. Press Reset switch on the left hand.
  4. Press Reset switch while holding down - keys.
    (or press Sub CPU Reset switch)

2.2.6 Changing parameters

For a description of how to change the parameters see the CONFIG program in Chapter 3, and section 2.2.3a. Details of which parameters are changed by the CONFIG program and which by the System Display can be found from table 2.2.

page 2-49

2.2.7 The Screen of the PX-8

When you view the LCD screen of the PX-8, you are looking at a window on a much larger screen. The screen displayed on the LCD is known as the real screen. This is 8 lines high by 80 columns. The operating system works with a much larger screen, a screen of up to 40 lines and 80 columns. The real screen then displays a window on this larger screen (the virtual screen), which is called the virtual screen window.


There are also four different screen modes (including a graphics mode) which show different types of display. In all but the graphics mode there are two vir-tual screens.
This section outlines the different screen modes and shows how to use them. Changing between different screen modes can be achieved using the CONFIG program described in Chapter 3. It is also possible to change the screen modes using BASIC commands, and the BASIC Reference Manual contains a practi-cal guide to the screen modes in section 2.14.

It is unlikely that you will use the different screen modes in the CP/M environ-ment unless a particular applications program has made use of them. However, there are certain benefits to be obtained by learning to use the tracking and non-tracking modes, and to understand the virtual screens. As these would be utilised mainly in screen mode 0, a detailed explanation is given in the follow-ing outline of this screen mode.

page 2-50

The Screen Modes

There are four screen modes possible with PX-8. Three of them are text only screens, and the fourth is a mixed text and graphics mode. The difference be-tween the modes is primarily the way the real screen presents the information written on the virtual screens.

a) Screen mode 0 (the 80 column text screen mode)

This screen mode has two virtual screens each with 80 columns. The number lines on these screens can be set by the user provided that the sum of the num-ber of lines does not exceed 48 and there are at least 8 lines (i.e. one real screen-ful of lines) on each screen.


The virtual screen window moves over the virtual screen to display a part of the virtual screen on the real screen. This movement is known as scrolling. When the real screen moves over the virtual screen, scrolling with the cursor, this is known as tracking mode. Tracking mode can be switched off by pressing the key ( + ). When this is done the cursor moves over the virtual screen while the real screen stays at the same place on the virtual screen. The real screen becomes locked in a particular position on the virtual screen.

The following illustration will show the effect of scrolling in the tracking and non-tracking modes. It assumes that the virtual screen size of 24 lines on each

page 2-51

screen has been set. The CONFIG program described in Chapter 3 can be used to check this and reset it if necessary.

Go to the System Display and switch off the MENU. Exit from the System Dis-play to display the CP/M command line.
If the screen is not clear, it may be cleared by pressing the key ( + ), or typing CTRL-L by holding down the key while pressing the key. In either case the display will show eL” next to the CP/M sys-tem prompt. Thus if the currently logged in drive is A:, the following will be displayed:


When the key is pressed, the screen will clear and show a question mark in the top left hand corner. This is because CP/M does not understand - , as a command. After printing a blank line the system prompt is printed again, with the cursor to the right of it.

Now obtain a directory of the utility ROM by typing "DIR C:" if the ROM is in ROM socket 2, or "DIR B:" if it is in ROM socket 1. For the purposes of this illustration it will be assumed that it is in ROM socket 2 as supplied.

The display will show:


Because only two lines and a new system prompt have been written on the screen, the screen has not needed to scroll. However if the command is typed again, the "?" will scroll off the top of the real screen, and show the following:

2-52-2 2-52-2 page 2-52

The "?" is still the first character on the virtual screen. This can be seen in e of two ways. Pressing the and cursor key will display the first lrnes of the virtual screen because these keys move the real screen backwards one page (i.e. one real screen) on the virtual screen. Pressing the space bar (or any other key) will return to the original display. Alternatively the screen can be scrolled up by pressing the and cursor key. Again pressing the space bar or another key will return the real screen to show the cursor.

To show the effect of this sequence of operations in non-tracking mode, first clear the screen again using - or the key. Then press the key ( + ). Nothing will appear to happen. Now obtain two directories of the utility ROM in drive C: by typing "DIR C:" as before. The screen will show:

Note how the "?" on the first line remains visible in contrast to the same se-quence of operations in the tracking mode. This time the cursor and CP/M system prompt has disappeared off the real screen. They are further down the virtual screen just outside the window. They can be seen by pressing the + cursor key to move the screen up. This leaves the real screen window locked on these particular eight lines, so that typing "DIR C:" again will write the directory outside the real screen. Pressing the key again will cause the tracking mode to be restored and the screen will move up to show the cur-sor, When returning to tracking mode the cursor is positioned in the centre of the screen and so the screen will appear as follows:

page 2-53

Now press the key ten times. This will almost reach the bottom of the virtual screen. Press the and key to move to the bottom of the virtual screen. Note that there are still two free lines of the virtual screen with nothing printed on them.

Move to the top of the virtual screen by pressing the and key twice. Note that the first character the "?" is still present. Lock the screen into non-tracking mode by means of the key. Now type "DIR C:" again. This will write the directory of disk C: on the bottom of the virtual screen next to the cursor, and then print a new CP/M system prompt. However, as there are not enough lines on the virtual screen the whole virtual screen must scroll up one line. This causes the window at the top of the screen to change. The line containing the "?" character is pushed off the cap of the virtual screen, and lost forever. The top 8 lines of the virtual screen are still displayed on the real screen, but they are 8 new lines now that scrolling has occurred. Return to track-ing mode by pressing the key again and the bottom of the virtual screen, containing the cursor will be shown, with the directory of drive C: and the new CP/M system prompt.

So far only one virtual screen has been used. It is possible to move onto the second virtual screen by using the and key, and back to the first virtual screen using the and key. The two screens can be written to independantly, although there is no guarantee that all applications software will allow you to use the second virtual screen or scroll or go into non-tracking mode.

Switch to the second virtual screen using the and keys. The screen should be blank. Type "DIR B:" and contents of the directory of the B: drive will be printed. If you switch back to the first virtual screen using the and keys, the screen will be exactly as you left it. Clear it with a - or by using the key and then go back to virtual screen 2 using the and key. Note that the display has not been changed.

One use of the two virtual screens is to store data. For example, frequently one needs to know the contents of the directory of a disk. Go to virtual screen 2, and print the directory of the disk there. If the program will allow it (and the CP/M utilities such as PIP will) you can easily look at the second screen to inspect the directory by using the and keys, and then return to the first virtual screen to continue with the program. In both cases the previ-ously displayed screen, normally where the cursor lies, will appear in the real screen area. page 2-54

It is not advisable to enter a program command on the second virtual screen if the previous command was executed on the first virtual screen.

b) Screen mode 1 (39 column split screen text mode)
This screen mode splits the real screen into two halves, each of 39 columns with a boundary of two characters in the centre of the screen. There are two virtual screens but they must both have the same number of lines. The number of lines in the virtual screens must be in the range 16 to 48. Only one virtual screen can be displayed at a time. The real screen can be thought of as a screen of 39 columns, 16 lines long which has been split into two blocks of eight lines which are displayed on the two halves of the real screen. The bottom of the left half of the screen is continued on the top of the right half of the screen.

vscreens 2-55

page 2-55

If the sequence of clearing the screen and printing two directories of the C: drive is performed with screen 1 turned on (it can be chosen by using the CON-FIG program described in Chapter 3), then the screen will show the following output.

vscreens 2-56

Tracking and non-tracking modes can be set with the SCRN key, and the two virtual screens can be displayed using the ¿crRL and + and ¿crRi and keys just as with screen mode 0.

c) Screen mode 2 (the dual screen mode)
In this screen mode, the real screen is divided into two halves. There are two virtual screens, and each of the virtual screens are displayed in the two halves of the real screen. While the contents of the two screens can be seen at the same time, they are also independent of one another, and so can be scrolled separately. They canot be set in the tracking and non-tracking mode independently.

The number of lines of the two virtual screens must be in the range 8 to 48, and must be the same in both virtual screens. The number of columns and the boundary character can be set by the user. The totalnumber of columns must equal 79, and there must be at least one column in one of the screens. The CON-FIG program described in Chapter 3, can be used to set these parameters.

page 2-56

vscreens 2-57

d) Screen mode 3 (the graphic screen mode)
This mode enables graphics to be displayed. Text can also be displayed on this screen. There is only one virtual screen whose size is the same as the size of the real screen. Thus scrolling the real screen over the virtual screen and setting the tracking and non-tracking modes do not apply.

page 2-57

vscreens 2-58

The screen allows individual dots of the screen to be lit (bit image mode). This is only possible by means of software. The most convenient way to understand this mode is to use BASIC. If this mode is used other than in BASIC, it will be with special applications software and the appropriate manual should be con-sulted for its use.

page 2-58