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GENERAL DESCRIPTION

The DAI Personal Computer is designed to provide the maximum capability that can economically be provided to an individual. The design is realised such that programs are loaded from a low cost audio cassette or a floppy disc. The results of program execution are output to the user via an antenna connector for PAL, SECAM or NTSC standard television receiver, The Graphical Sound Generation also outputs two tracks of separated sound for left and right stereo connections, and the sound channel of the television.

The resources of the DAI Personal Computer are partitioned into four segments; the Microcomputer Section, Programmable Graphical Video Section, the Sound Generator Section and the I/0 Section. To optimise usage of components within the design, considerable overlay of logic usage exists within the system. Figure 1 is a logical block diagram of the DAI Personal Computer.

The resident software is comprised of six major modules, Basic Interpreter, Math Package, Screen Driver Module, Keyboard Scan + Encode Routine, the Machine Language Utility and the General House- keeping Module.

The Basic Interpreter incorporates most of the features found in other Personal Computers as well as special statements to control the video graphics and sound generator and interface with the Machine Language Utility as well as assist with generation and editing of source programs. In order to obtain the minimum possible execution time the design of the Basic System is such that it functions as a quasi-interpreter. When the user types in his source program it is compressed and encoded into a special "run-time" code so that the Execution Routine has the smallest possible amount of work left to do.

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The Math Package is broken into an Integer Math Module and a Floating Point Math Module. The integer module performs only basic operations as +, -, multiply etc., while the Floating Point Math Module provides these plus transcendental functions.
Integer variables are calculated to nine digit resolution and floating point variables to 6 digit resolution. The Math Package handles floating point numbers in the range &plusmin;10-18 to &plusmin;1018 and zero. When the Scientific Math option is inserted into its socket the Math Package automatically uses it for calculations instead of the software calculation modules.

The Screen Driver Module is responsible for arranging the data in memory to give a correct picture in all modes. It also handles the changing of screen colours, the drawing facilities (DOT, FILL, DRAW) and other screen-related facilities.
The Keyboard of the DAI Personal Computer is a simple matrix of 56 keys connected in an 8 x 7 matrix. The Keyboard Scan + Encode Routine scans the keyboard at fixed time intervals, detects key depressions and encodes a specific key according to a look-up table. Since the keyboard of the DAI Personal Computer has been constructed in this fashion it is possible to provide DAI Personal Computers with other configurations and codes. The keyboard driver software provides for a 3 key rollover mechanism.

The Machine Language Utility is a complete set of keyboard and subroutine callable functions that permit and assist the generation, loading, de-bugging, and execution of machine language programs and subroutines. The control subroutines and housekeeping subroutines of this module allow direct interface between BASIC programs and machine language program and subroutines. An unlimited number of machine language subroutines may be called by a BASIC program.
The General Housekeeping Module is a set of routines that are shared by other modules, providing for instance, the control of memory bank switching. This allows the 8080A microprocessor to operate with 72K bytes of memory instead of the 64K normally.

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Summary of features

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Microcomputer
8080A microprocessor running at 2MHz.
8K, 12K, 32K, 36K, 48K RAM memory configurations
24K PROM/ROM capability (software bank switched)
Memory mapped I/0
AMD 9511 math chip support logic
Hardware random number generator
Stack overflow detect logic.

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I/0 Devices
ASCII Keyboard
PAL/SECAM/NTSC/VIDE0 TV connection via antenna input (color and B/W)
Sound channel audio modulated on TV signal.
Dual low cost Audio cassette input and output with stop(start control.
Stereo hi-fi output channels
Left and Right garne paddle inputs (6 controls)
Interface bus (DAI's DCE -BUS) to:
floppy disk controller
printer controller
standard interface cards (DAI's RWC family)
IEEE bus adaptor
communication interconnections
control connection
prom programming
special interfaces
analog input and output RS232 Interface
Programmable baud rates
Terminal or modem function

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Graphical Video
Character screen mode (66 characters x 24 lines normally 11/22/44/66
characters + 13 to 32 lines possible)
16 colors or grey scales
Multiple resolution graphics modes (software selectable)

65 x88
130 x 176
260 x 352
(Intermixed mode screens of lines of characters and graphics are possible).
True "square" graphics.

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Graphical Sound
3 independently programmable frequencies
1 programmable noise generator
Amplitude and frequency software selectable

smooth music
random frequencies
enveloped sound
vocal sound generator

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Resident Software
Extended Highspeed BASIC interpreter
Full floating point scientific math commands,
Hardware scientific functions automatically used if math module present.
Graphical video commands

full graphic plotting
arbitrary line specification
arbitrary dot placement
filling of arbitrary rectangles
Graphical sound commands
predetermined volume envelope specification
individual specification of frequency

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individual specification of volume
individual specification of tremolo
individual specification of glissando
Machine Language Utility.

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Compatible System Software
DAI Assembler
8080A Standard software support
FORTRAN Compiler support
MDS/Intellec non-disc software support.