Emulator Enhanced Z80 Instructions v6.10
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Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 20H
Description:
Multiply register D by register E and return result in DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: None
Example:
100
LD D,15H ; load D with
15h
110
LD
E,40H ; load E with 40h
120 DEFB EDH
; multiply 8 bit unsigned values
130 DEFB 20H
After execution DE will contain 540h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 21H
Description:
Multiply register HL by register DE and return result in HL:DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: None
Example:
100
LD
HL,2015H ; load HL with
2015h
110 LD
DE,0140H ; load DE with
140h
120 DEFB EDH
; multiply 16 bit
unsigned values
130 DEFB 21H
After execution HL will contain 28h and DE will contain 1A40h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 22H
Description:
Divide register HL by register DE and return result in HL and remainder in DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if divide by zero; reset otherwise
C: Set if divide by zero; reset otherwise
Example:
100
LD
HL,2175H ; load HL with 2175h
110
LD
DE,40H ; load DE with 40h
120 DEFB EDH
; divide 16 bit
unsigned values
130 DEFB 22H
After execution HL will contain 85h and DE will contain 35h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 23H
Description:
Divide registers HL:DE by registers IX:IY and return result in HL:DE and remainder in IX:IY.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if divide by zero; reset otherwise
C: Set if divide by zero; reset otherwise
Example:
100
LD DE,2175H
; load HL:DE with 402175h
110
LD
HL,40H
120
LD IX,4578H
; load IX:IY with 14578h
130 LD
IY,0001H
120 DEFB EDH
; divide 32 bit
unsigned values
130 DEFB 23H
After execution HL:DE will contain 32h and IX:IY will contain 9005h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 24H
Description:
Perform a signed multiply of register D and register E and return result in DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if overflow; reset otherwise
C: Set if overflow; reset otherwise
Example:
100
LD D,15H ; load D with 15h
110
LD E,40H ; load E with 40h
120 DEFB
EDH ; multiply 8 bit signed
values
130 DEFB 24H
After execution DE will contain 540h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 25H
Description:
Perform a signed multiply of register HL by register DE and return result in HL:DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if overflow; reset otherwise
C: Set if overflow; reset otherwise
Example:
100
LD
HL,2015H ; load HL with 2015h
110
LD DE,0140H ; load DE with
140h
120 DEFB
EDH ; multiply 16 bit
signed values
130 DEFB 25H
After execution HL will contain 28h and DE will contain 1A40h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 26H
Description:
Perform a signed divide of register HL by register DE and return result in HL and remainder in DE.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if overflow or divide by zero; reset
otherwise
C: Set if overflow or divide by zero; reset otherwise
Example:
100 LD
HL,2175H ; load HL with 2175h
110 LD
DE,40H ; load DE with
40h
120 DEFB EDH
; divide 16 bit signed values
130 DEFB 26H
After execution HL will contain 85h and DE will contain 35h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 27H
Description:
Divide registers HL:DE by registers IX:IY and return result in HL:DE and remainder in IX:IY.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
P/V Set if overflow or divide by zero; reset
otherwise
C: Set if overflow or divide by zero; reset otherwise
Example:
100
LD DE,2175H ; load HL:DE
with 402175h
110
LD HL,40H
120 LD
IX,4578H ; load IX:IY with
14578h
130 LD
IY,0001H
120 DEFB EDH
; divide 32 bit signed
values
130 DEFB 27H
After execution HL:DE will contain 32h and IX:IY will contain 9005h
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 28H
Description:
Shell to DOS and execute the command pointed to by register HL. If the command is null (only a zero terminator) then this function shells to a DOS prompt. If Z flag is set then the command executed ok and register BC contains return code else register A contains the error number.
If register A is non-zero then a push any key to continue message will be displayed when the command finishes before the TRS-80 screen is re-displayed.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if shell command ok; reset otherwise
Example:
100
LD
HL,CMD ; load HL with address of command
110 LD
A,01H ; display push any key to continue
message
120 DEFB EDH
; execute shell command
130 DEFB 28H
.
.
.
200 CMD DEFM
‘DIR’ ; zero terminated
command to execute
210 DEFB 00H
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 29H
Description:
This function allows access to the PC mouse, there are 6 sub-functions.
Function 1: Get X corr, Y corr and buttons
Before:
B
= 1
After:
HL
= mouse cursor X value
DE
= mouse cursor Y value
A
= button status
bit
0 reset if right button pushed
bit 1 reset if middle button pushed (left
& right pushed for 2 button mice)
bit
2 reset if left button pushed
Function 2: Set X corr, Y corr and set button status
Before:
B
= 2
C
= button status
bit
0 set or reset right button pushed
bit
1 set or reset left button pushed
After:
flags
= Z flag set if successful
Function 3: Get max X corr, Y corr and sensitivity
Before:
B
= 3
After:
HL
= mouse max X corr value
DE
= mouse max Y corr value
A
= sensitivity (0 to 3); 3 is most sensitive
Function 4: Set max X corr, Y corr and sensitivity
Before:
B
= 4
HL
= mouse max X corr value
DE
= mouse max Y corr value
A
= sensitivity (0 to 3); 3 is most sensitive
After:
flags
= Z flag set if successful
Function 5: Get mouse type
Before:
B
= 5
After:
A
= mouse type (0=two button, 1=three button)
Function 6: Get X corr, Y corr and buttons
Before:
B
= 6
After:
HL =
mouse cursor X value (0 - 1024)
DE =
mouse cursor Y value (0 -1024)
C = buttons currently pushed
bit
4 set if right button pushed
bit
5 set if left button pushed
B
= buttons pushed since last reset using function #2
bit
4 set if right button was pushed
bit
5 set if left button was pushed
M CYCLES: 4 T STATES:
4 4 MHZ E.T.: 1.00
Condition Bits Affected: set according to function type
Example:
100
LD B,01H ; load B with
get X, Y and buttons command
110 DEFB EDH
; execute mouse command
120 DEFB 29H
130 .
; HL contains X cursor value
140 .
;
DE contains Y cursor value
150 .
;
A contains button status
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2AH
Description:
Read the PC port pointed to by register HL into register A.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
LD HL,0201H ; read PC game
port
110 DEFB EDH
120 DEFB 2AH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2BH
Description:
Write register A to the PC port pointed to by register HL.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
LD A,0FFH ; load
A with FFh
110 LD
HL,0201H ; write register A
to PC game port
120 DEFB EDH
130 DEFB 2BH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2CH
Description:
Read the PC memory address pointed to by register DE:HL into register A. Register DE contains the PC segment and HL contains the address within the segment.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
LD
DE,0040H ; set segment to
0040h
110 LD
HL,0000H ; set address to
0000h
130 DEFB EDH
; read address
0040h:0000h into A
130 DEFB 2CH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2DH
Description:
Write register A to the PC memory address pointed to by register DE:HL. Register DE contains the PC segment and HL contains the address within the segment.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
LD
A,0FFH ; load A
with FFh
110 LD
DE,0040H ; set segment to
0040h
120 LD
HL,0000H ; set address to
0000h
130 DEFB
EDH ; read address
0040h:0000h into A
140 DEFB 2DH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2EH
Description:
Set CPU speed to value defined by register A.
bits 0-1
00 2/1.77mhz
01 4mhz
10 1mhz
11 8mhz
bit 2 Turbo speed if set
bit 3 Speed port locked if set
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
LD A,0CH
; Set turbo
speed & lock port
110 DEFB EDH
; execute
speed set command
120 DEFB 2EH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 2FH
Description:
Get CPU speed and return value in register A.
bits 0-1
00 2/1.77mhz
01 4mhz
10 1mhz
11 8mhz
bit 2 Turbo speed if set
bit 3 Speed port locked if set
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected: none
Example:
100
DEFB EDH
; get
current CPU speed
110 DEFB 2FH
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 30H
Description:
Opens the file specified by the path pointed to by HL. The path must conform to PC standards and be zero terminated. The BC register is used to define the type of file access. If the file is being created the DE register is used to define the access permission.
If the open is successful the Z flag is set and the file’s channel is returned in the DE register else the Z flag is reset, DE is loaded with FFFFh and the A register contains the error number.
File Access:
bits 0-1 of BC:
00 open file read only
01 open file write only
10 open file read/write
bit 6 of BC create file if doesn't exist
(create)
bit 7 of BC used only with bit 6 set. If file exists, an error is
returned
bit 9 of BC if file exists then file is truncated (truncate)
bit 10 of BC the file pointer will be set to the end of the file
prior to each write (append)
File Access Permission:
bit 7 of DE if set, permission to write to file
bit 8 of DE if set, permission to read to file
only has effect when file is being created. To allow read & write access both bits must be set.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file opened ok; reset otherwise
Example:
100
LD
HL,PCFN ; load HL with address of
filespec
110
LD
BC,0241H ; create or truncate file & open
in write only mode
120 LD
DE,0180H ; create file
with read & write permission
130 DEFB EDH
; execute open
command
140 DEFB 30H
150
JR
NZ,ERROR ; jump if error
160 LD
(CHAN),DE ; save channel number of I/O
.
.
.
200 PCFN DEFM ‘PCFILE.CMD’ ; zero
terminated filespec to open
210 DEFB 00H
220 CHAN DEFW
0000H ; saved
channel number
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 31H
Description:
Closes file on channel specified by the DE register. The Z flag is set if close successful else the Z flag is reset and the A register contains the error number.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file closed ok; reset otherwise
Example:
100
LD
DE,(CHAN) ; load DE with channel
number of file to close
110 DEFB EDH
; execute close command
120 DEFB 31H
130 JR
NZ,ERROR ; jump if error
.
.
.
200 CHAN DEFW
0000H ; saved channel number
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 32H
Description:
Read the number of bytes defined by register BC into the buffer area pointed to by register HL from the channel defined by register DE. If the Z flag is set then the read was successful, register BC will contain the number of bytes actually read and the buffer will contain the data read. If BC is less than the value before execution of the instruction and there was no error then the end of file was reached. If an read error occurred then the Z flag is reset and BC will contain the number of bytes actually read, & register A will contain the error number.
It is possible to read 0001h to FFFEh bytes in a single read.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file read ok; reset otherwise
Example:
100
LD
HL,(BUFF) ; load HL with
pointer to buffer
110 LD
DE,(CHAN) ; load DE with
channel number of file to read from
120
LD
BC,0100H ; load BC with bytes to read
130 DEFB EDH
; execute read
command
140 DEFB 32H
150 JR
NZ,ERROR ; jump if
error
160 LD
A,B
; check if all
bytes read
170 CP
01H
180
JR
NZ,EOF ; jump if not
190
LD
A,C
200 CP
00H
210 JR
NZ,EOF ;
jump if not
.
.
.
300 BUFF DEFS
0100H ; define a 256 byte
buffer
310 CHAN DEFW 0000H
; saved channel number
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 33H
Description:
Write the number of bytes defined by register BC from the buffer area pointed to by register HL to the channel defined by register DE. If the Z flag is set then the write was successful, register BC will contain the number of bytes actually read and the buffer will be unchanged. If an read error occurred then the Z flag is reset and BC will contain the number of bytes actually written & register A will contain the error number.
It is possible to write 0001h to FFFEh bytes in a single write. If register BC contains 0000h then the file will be truncated at the current file pointer location.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file write ok; reset otherwise
Example:
100
LD
HL,(BUFF) ; load HL with pointer to buffer
110 LD
DE,(CHAN) ; load DE with channel number
of file to write to
120 LD
BC,0100H ; load BC with bytes to
write
130 DEFB EDH
; execute write command
140 DEFB 33H
150 JR
NZ,ERROR ; jump if error
.
.
.
300 BUFF DEFS 0100H ;
define a 256 byte buffer
310 CHAN DEFW 0000H ; saved
channel number
Operation: Emulator Instruction (DOS Int 21h Function 42h)
Format:
Opcode Operands
DEFB EDH
DEFB 34H -or- 3DH
Description:
Set the file position to the 32 bit signed integer value pointed to by register HL using the method defined in register C. If successful the Z flag is set and the 32 bit signed integer value pointed to by HL is updated with the new file position. If an error occurs then the Z flag is reset and register A contains the error number.
Using method 1 or 2 it is possible to position beyond the start of the file without an error, an error will occur upon a subsequent read or write to the file.
Method code:
C = 0 absolute byte offset from beginning of
file (always positive double integer)
C = 1 byte offset from current location (positive or negative
double integer)
C = 2 byte offset from end of file (positive or negative double
integer)
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file seek ok; reset otherwise
Example:
100
LD
HL,0100H ; save new file position (00000100h)
110 LD
(BUFF),HL
120
LD
HL,0000H
130
LD
(BUFF+2),HL
140
LD HL,(BUFF)
; load HL with pointer to buffer (at least 4 bytes)
150
LD
DE,(CHAN) ; load DE with channel number of file to
write to
160
LD
C,00H ; load BC with method
code (absolute)
170 DEFB
EDH ; execute
seek command
180 DEFB
34H
190 JR
NZ,ERROR ; jump if
error
.
.
.
300 BUFF DEFS
0100H ; define a 256 byte
buffer
310 CHAN DEFW 0000H
; saved channel number
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 35H
Description:
Builds error message in buffer pointed to by register HL for the error number in register A. If the length of the buffer is not able to hold the entire message the message is truncated to fit and register A contains range error, else register A is set to zero.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: always set
Example:
100
LD
DE,(CHAN) ; load DE with channel
number of file to close
110 DEFB
EDH ;
execute close command
120 DEFB
31H
130 JR
NZ,ERROR ; jump if error,
error number is in register A
.
.
.
200 ERROR LD HL,ERRMSG ;
load HL with pointer to message buffer
210 DEFB
EDH ;
execute error message command
220 DEFB
35H ; upon
return the error message is in buffer, zero terminated
.
.
.
300 ERRMSG
DEFS 0100H ;
define a 256 byte buffer
310 CHAN DEFW 0000H
; saved channel number
Operation: Emulator Instruction (DOS Int 21h Function 4Eh)
Format:
Opcode Operands
DEFB EDH
DEFB 36H
Description:
Given a file specification in the form of an ASCIIZ string, searches the default or specified directory on the default or specified disk drive for the first matching file. If a match is found the buffer pointed to by register HL will be loaded with the file data found and the Z flag is set, else the Z flag is reset and register A contains the error number.
Wildcard characters ? and * are allowed in the filename. Files found are based on the attributes set in the DE register.
WARNING: Buffer must be at least 43 bytes long.
File Attributes:
bit 0 of DE read-only
bit 1 of DE hidden
bit 2 of DE system
bit 3 of DE volume labels (if set only volume labels are
returned)
bit 4 of DE subdirectory; entry excluded from normal searches
bit 5 of DE archive
Buffer Structure:
bytes 0-20 reserved for DOS on
subsequent calls
byte 21 attribute of
matching file
bytes 22-23 file time
bytes 24-25 file date
bytes 26-29 file size (32 bit integer)
bytes 30-42 filename & extension in form of ASCIIZ string
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file match found; reset otherwise
Example:
100
LD
HL,BUFF ; load HL with
address of filespec
110 LD
BC,43 ;
buffer must be 43 bytes long
120 LD
DE,01H ; find all
normal and read only files
130 DEFB EDH
; execute findfirst command
140 DEFB 36H
150
JR
NZ,ERROR ; jump if no matching files
.
;
buffer filled with directory entry, filename starts at byte 30
.
.
200 BUFF DEFM ‘*.*’
; zero terminated filespec to search for
210 DEFB 00H
220 DEFS 39
; buffer must be 43
bytes long
Operation: Emulator Instruction (DOS Int 21h Function 4Fh)
Format:
Opcode Operands
DEFB EDH
DEFB 37H
Description:
Assuming a successful previous FINDFIRST function the FINDNEXT function finds the next file in the default or specified directory on the default or specified disk drive that matches the original file specification. If a match is found the buffer pointed to by register HL will be loaded with the file data found and the Z flag is set, else the Z flag is reset and register A contains the error number.
WARNING: Buffer must be at least 43 bytes long.
Buffer Structure:
bytes 0-20 reserved for DOS on subsequent calls
byte 21 attribute of matching file
bytes 22-23 file time
bytes 24-25 file date
bytes 26-29 file size (32 bit integer)
bytes 30-42 filename & extension in form of ASCIIZ string
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file match found; reset otherwise
Example:
100
LD
HL,BUFF ; load HL with address of filespec
110
LD
BC,43 ; buffer must be 43 bytes long
120 LD
DE,01H ; find all normal
and read only files
130 DEFB
EDH ; execute findnext command
140 DEFB 37H
150 JR
NZ,ERROR ; jump if no more matching
files
.
;
buffer filled with directory entry,
.
;
filename starts at byte 30
.
200 BUFF DEFS
43 ; buffer must
be 43 bytes long
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 39H
Description:
Open and load the object file specified by the path pointed to by HL. The path must conform to PC standards and be zero terminated.
If the load is successful the Z flag is set and if the object file contained an execution address then the C flag is also set and register BC contains the execution address. If the file was not found or was not a valid object file then the Z flag is reset and the A register contains the error number.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file opened ok; reset otherwise
Example:
100
LD
HL,PCFN ;
load HL with address of filespec
110 DEFB EDH
; execute
load command
120 DEFB 39H
130
JR
NZ,ERROR ; jump if error
140 JR
NC,EXIT ;
exit if no exec address found
150 DI
;
disable interrupts
150 PUSH BC
;
push exec address on stack
160
RET ;
execute loaded program
.
.
.
200 PCFN DEFM ‘GALAXY.CMD’ ; zero
terminated filespec to load
210 DEFB 00H
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 3AH
Description:
Changes the current drive and directory to the path pointed to by the register HL. If the command is successful the Z flag is set else the Z flag is reset and the A register contains the error number.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file chdir ok; reset otherwise
Example:
100
LD
HL,BUFF ; load HL with
address of path
110 DEFB
EDH ;
execute chdir command
120 DEFB 3AH
130
JR
NZ,ERROR ; jump if error
.
.
.
200 BUFF DEFM ‘C:\TRS80’ ; zero
terminated path to change to
210 DEFB 00H
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 3BH
Description:
Gets the current working directory and drive. The path and drive are stored in the buffer pointed to by the register HL. If the command is successful the Z flag is set else the Z flag is reset and the A register contains the error number. If the full path is longer than the buffer an error will occur.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file getdir ok; reset otherwise
Example:
100
LD
HL,BUFF ; load HL with address of
path
110 LD
BC,128 ; save length of
buffer
120 DEFB EDH
; execute getdir command
130 DEFB 3BH
140
JR
NZ,ERROR ; jump if error
.
; upon return the
path is in buffer,
.
;
zero terminated
.
200 BUFF DEFS 128
; create a buffer long
enough to hold path
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 3EH
Description:
Opens the file specified by the path pointed to by HL. The path must conform to PC standards and be zero terminated. The BC register is used to define the type of file access. If the file is being created the DE register is used to define the access permission.
If the open is successful the Z flag is set and the file’s channel is returned in the DE register else the Z flag is reset, DE is loaded with FFFFh and the A register contains the error number.
Unlike the OPEN command this command is used in writing floppy & hard disk drivers for TRS-80 DOS's.
If no path is given the current floppy path will be used (set in the floppy selection screen). If no extension is given the extension .DSK will be used.
If 'HARDX-YY' (where X= '1', '3' or '4' and YY= a value of 0-7) is given as the filename then one of the 8 hard disk filenames (16 in the Model 3/4 emulator) defined in the configuration screen will be opened.
File Access:
bits 0-1 of BC:
00 open file read only
01 open file write only
10 open file read/write
bit 6 of BC create file if doesn't exist
(create)
bit 7 of BC used only with bit 6 set. If file exists, an error is
returned
bit 9 of BC if file exists then file is truncated (truncate)
bit 10 of BC the file pointer will be set to the end of the file
prior to each write (append)
File Access Permission:
bit 7 of DE if set, permission to write to file
bit 8 of DE if set, permission to read to file
NOTE: Only has effect when file is being created. To allow read & write access both bits must be set.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file opened ok; reset otherwise
Example:
100
LD
HL,HARD ; load HL with
address of filespec
110
LD
BC,0002H ; open in read/write mode
120 DEFB EDH
; execute open command
130 DEFB 3EH
140 JR
NZ,ERROR ; jump if error
150 LD
(CHAN),DE ; save channel number of
I/O
.
.
.
200 HARD DEFM ‘HARD4-0’ ; open
defined Model 4 mode hard drive #0
210 DEFB 00H
220 CHAN DEFW 0000H
; saved channel number
If in the configuration screen the Model 4 drive #0 is defined as:
C:\TRS-80\LDOS0.HDV
Then, if the file exists, it will be opened for read/write I/O and the channel number returned in DE.
Operation: Emulator Instruction
Format:
Opcode Operands
DEFB EDH
DEFB 3FH
Description:
Closes file on channel specified by the DE register or closes all open files if DE=FFFFh. The Z flag is set if close successful else the Z flag is reset and the A register contains the error number.
If DE=FFFFh then no error is reported even if no files are closed.
M CYCLES: 4 T STATES: 4 4 MHZ E.T.: 1.00
Condition Bits Affected:
Z: Set if file closed ok; reset otherwise
Example:
100
LD
DE,FFFFH ; load DE FFFFh to close
all files
110 DEFB EDH
; execute close command
120 DEFB 3FH
130
JR
NZ,ERROR ; jump if error
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