CP/M/CPM_CDROM.iso/simtel/sigm/vols000/vol073/prom08u.asm

Assembly Source File | 1984-04-29 | 14.1 KB | 886 lines

;
;****************************************************************
;*                                *
;*                                *
;*        DRIVER UTILITY FOR SD SYSTEMS            *
;*          PROM-100 EPROM PROGRAMMER            *
;*            2708 VERSION                *
;*                                *
;*                                *
;****************************************************************
;
;
;    Modified by :    Bill Bolton
;            Software Tools
;            P.O. Box 80
;            Newport Beach
;            NSW, 2106
;
;    Dec 29, 1979    Initial bugs removed
;
;    Jan  3, 1980    Comments added and minor improvements
;
;    Jan  4, 1980    2716 file created from 2708 file
;
;    Jan 16,    1980    First PROM address not programmed debug
;
;    Jan 22, 1982    8080 version created and SPEED equate added
;            plus other minor internal changes
;
;    Jan 25, 1982    8080 2708 version created from 2716 version
;
WBOOT    EQU    0
BDOS    EQU    00005H        ;BDOS ENTRY ADDRESS
FCB    EQU    0005CH        ;DEFAULT FILE CONTROL BLOCK
OPEN    EQU    15
SETDMA    EQU    26
ATTRIB    EQU    471BH        ;ADM VIDEO ATTRIBUTE LEAD-IN
DATA    EQU    068H        ;PROM-100 DATA PORT
LADD    EQU    069H        ;PROM-100 LOW ADDRESS PORT
HACTL    EQU    06AH        ;PROM-100 CONTROL PORT
SPEED    EQU    6        ;PROCESSOR SPEED IN MHZ
ACR    EQU    0DH        ;ASCII CARRAIGE RETURN
ALF    EQU    0AH        ;ASCII LINE FEED
;
    TITLE    'PROM16 - 8080 VERSION FOR CP/M'
;
    MACLIB    MACRO3        ;Use Software Tools special macros
;
    ORG    0100H
;
;
    LXI    SP,SPVAL
    LXI    H,MESG1        ;SIGN ON MESSAGE
    CALL    PTXT        ;PRINT IT
    MVI    A,080H        ;INIT BUFFER COUNT TO FULL
    STA    BUFCNT        ;STORE IT
    XRA    A        ;RESET A TO 0
    STA    OPENFL        ;RESET FILE OPEN FLAG
INITIAL:
    LXI    SP,SPVAL
    XRA    A
    OUT    HACTL        ;INIT PROM-100 BOARD
    CALL    CRLF
    LXI    H,MESG2        ;READY TO LOAD MESSAGE
    CALL    PTXT
    LXI    H,0        ;RESET HL
    SHLD    COUNT        ;RESET COUNT
    CALL    YORN        ;YES OR NO?
    JNC     READ2        ;NO, GO ASK IF A PROM
                ;IS TO BE READ
;
FILEOPN:
    CALL    CRLF
    LDA    OPENFL        ;GET FILE OPEN FLAG
    ORA    A        ;IS FILE OPEN?
    JNZ    FILER        ;YES, CONTINUE TO READ IT
    PUSH    H
    PUSH    D
    PUSH    B
    MVI    C,OPEN        ;OPEN FILE
    LXI    D,FCB        ;FCB ADDRESS
    CALL    BDOS
    POP    B
    POP    D
    POP    H
    CPI    0FFH        ;SUCESSFUL OPEN?
    JNZ    FILER        ;YES, GO READ IT
    LXI    H,MESG7        ;NO, FILE NOT FOUND
    CALL    PTXT
    JMP    EXIT         ;BACK TO CP/M
;
FILER:
    PUSH    D
    PUSH    B
    MVI    C,SETDMA    ;SET DISK BUFFER
    LXI    D,00080H    ;BUFFER ADDRESS
    CALL    BDOS
    POP    B
    POP    D
    LXI    H,MESG3        ;LOAD & BYTES MESSAGE
    CALL    PTXT
    CALL    SCAN$OP        ;GET OPERANDS FROM KEYBOARD
    LDA    NXCHAR        ;GET FINAL CHARACTER
    CPI    '.'        ;IS IT ENTRY ABORT CHAR?
    JZ     FILEOPN        ;YES, REPROCESS THE LOOP
    LXI    H,MESG9        ;NO, LOAD START MESSAGE
    CALL    PTXT
    LHLD    OPR1        ;POINT TO FIRST OPERAND
    CALL    PADDR        ;PRINT IT IN HEX
    CALL    CRLF
    CALL    HXREC        ;GET START OF NEXT HEX RECORD
    PUSH    H
    LDED    OPR1        ;GET MEM START ADDRESS
    LDA    OPCNT        ;GET NUMBER OF OPS ENTERED
    ANA    A        ;DETERMINE IF ZERO?
    JZ     FILER1        ;YES, LOAD FILE AT OWN ADDRESS
    DSUB            ;FORM LOAD OFFSET INTO MEMORY
    PUSH    H        ;COPY OFFSET
    POP    D        ; INTO DE
FILER1:
    POP    H        ;GET FILE START ADDRESS
    SDED    OFFSET        ;(OFFSET = 0 IF NO OPERAND)
    JMP    FILER3
;
FILER2:
    CALL    HXREC
FILER3:
    LDED    OFFSET        ;GET LOAD OFFSET
    ORA    A
    DSUB            ;FORM LOAD ADDRESS
LOADLP:
    CALL    HEXBIN        ;GET A BYTE
    MOV    M,A        ;PUT INTO MEMORY
    SHLD    LDPOINT        ;SAVE LOAD ADDRESS POINTER
    INX    H        ;BUMP THE LOAD ADDRESS
    PUSH    H
    LHLD    COUNT
    INX    H        ;BUMP THE LOAD COUNT
    SHLD    COUNT
    POP    H
    DCX    B        ;BC < NUMBER OF BYTES IN HEX RECORD
    MOV    A,B
    ORA    C
    JNZ    LOADLP
    CALL    HEXBIN        ;FETCH HEX RECORD CHECKSUM
    XRA    A        ;RESET A
    ADD    C        ;CHECKSUM ERROR?
    JZ     ENDCHK        ;NO, CHECK FOR END
    PUSH    H        ;YES, SAVE THE ADDRESS
    LXI    H,MESG10    ;CHECKSUM ERROR MESSAGE
    CALL    PTXT
    POP    H        ;RESTORE THE ADDRESS
    CALL    PADDR        ;PRINT ERROR ADDRESS
ENDCHK:
    LHLD    COUNT        ;COUNT OF BYTES LOADED
    LBCD    OPR2        ;NUMBER OF BYTES REQUIRED
    DCX    H
    DCX    B
    ANA    A
    BSUB            ;MORE BYTES TO LOAD?
    JC     FILER2        ;YES, GET THEM
;
LDEND:
    LXI    H,MESG11    ;LOAD END ADDR MESSAGE
    CALL    PTXT
    LHLD    LDPOINT        ;GET LOAD END ADDRESS
    CALL    PADDR        ;PRINT HEX ADDRESS
;
PPG10A:
    CALL    CRLF
    LXI    H,MESG4        ;READY TO PROG MESSAGE
    CALL    PTXT
    CALL    YORN        ;YES OR NO?
    JNC     EXIT        ;NO, EXIT
;
PPG11:
    CALL    CRLF
    LXI    H,MESG5        ;YES, MEM START ETC. MESSAGE
    CALL    PTXT
    CALL    SCAN$OP        ;GET OPERANDS
    LDA    NXCHAR
    CPI    '.'        ;ENTRY ABORT CHARACTER?
    JZ     PPG11        ;YES, REPROCESS LOOP
    JMP    PROG         ;NO, GO PROGRAM EPROM
;
;
; LOOKS FOR START OF A HEX RECORD AND RETURNS
; FIRST DATA BYTE IN A, BYTE COUNT IN B &
; RECORD LOAD ADDRESS IN HL
;
;
HXREC:
    CALL    BUFFR        ;GET AN ASCII BYTE
    CPI    ':'        ;IS IT HEX RECORD START?
    JNZ    HXREC        ;NO, KEEP LOOKING
    XRA    A        ;RESET A
    MOV    C,A        ;RESET C
    CALL    HEXBIN        ;GET A 'HEX' BYTE
    ANA    A        ;IS IT 0?
    JZ     HXREC1        ;YES, MUST BE AT END
    MOV    B,A        ;NO, # BYTES IN HEX RECORD
    CALL    HEXBIN
    MOV    H,A        ;HI BYTE OF LOAD
    CALL    HEXBIN
    MOV    L,A        ;LO BYTE OF LOAD
    CALL    HEXBIN        ;GET FIRST DATA BYTE
    RET
;
HXREC1:
    POP    PSW
    JMP    LDEND
;
;
; DETERMINE IF Y, N OR ABORT ANSWER
;
;
YORN:
    CALL    ECHO
    CPI    '.'
    JZ     EXIT
    ORA    A
    CPI    'N'
    RZ
    CPI    'Y'
    JNZ    YORN
    STC
    RET
;
;
; CONSOLE STATUS, INPUT AND OUTPUT
;
;
CONSTAT:
    PUSH    H
    PUSH    D
    PUSH    B
    MVI    C,11
    CALL    BDOS
    POP    B
    POP    D
    POP    H
    ORA    A
    RET
;
CONIN:
    PUSH    H
    PUSH    D
    PUSH    B
    MVI    C,1
    CALL    BDOS
    POP    B
    POP    D
    POP    H
    MOV    C,A        ;NEED A & C TO RETURN CHAR
    RET
;
CONOUT:
    PUSH    H
    PUSH    D
    PUSH    B
    MOV    E,C
    MVI    C,2
    CALL    BDOS
    POP    B
    POP    D
    POP    H
    MOV    C,E        ;NEED C TO RETURN CHAR
                ;SENT
    RET
;
;
; CLOSE FILE AND EXIT BACK TO CP/M
;
;
EXIT:
    XRA    A
    OUT    HACTL
    CALL    CRLF
    LDA    OPENFL
    ORA    A
    JZ     WBOOT
    MVI    C,16
    LXI    D,FCB
    CALL    BDOS
    JMP    WBOOT
;
;
; PRINT VALUE IN ACCUMULATOR AS AN ASCII 'HEX' VALUE
;
;
PADDR:
    MOV    A,H        ;HI BYTE OF ADDRESS
    CALL    PACC        ;PRINT A AS HEX VALUE
    MOV    A,L        ;LO BYTE OF ADDRESS
    JMP    PASP         ;PRINT<A, ' ' CRLF
;
;
MESG1:
    DB    ACR,ALF
    DB    'Software Tools PROM-100 Driver utility for 2708 EPROMs'
    DB    ACR,ALF
    DB    'Version 1.13 for '
    DB    SPEED + '0',' MHz Z80/8080, January 1982'
    DB    ACR,ALF
    DB    '$'
;
MESG2:
    DB    'Ready to load a hex file (Y/N)? '
    DB    '$'
;
MESG3:
    DB    'Load address, Number of bytes to load : '
    DB    '$'
;
MESG4:
    DB    'Ready to program a PROM  (Y/N)? '
    DB    '$'
;
MESG5:
    DB    'Memory start, Memory end, PROM start  : '
    DB    '$'
;
MESG6:
    DB    'Ready  to  read  a  PROM (Y/N)? '
    DB    '$'
;
MESG7:
    DB    ACR,ALF
    DW    ATTRIB
    DB    '4'
    DB    ' FILE NOT FOUND '
    DW    ATTRIB
    DB    '0'
    DB    '$'
;
MESG8:
    DB    ACR,ALF
    DW    ATTRIB
    DB    '4'
    DB    ' Attempting to read past end of disk file '
    DW    ATTRIB
    DB    '0'
    DB    '$'
;
MESG9:
    DB    ACR,ALF
    DB    'Load start address = '
    DB    '$'
;
MESG10:
    DW    ATTRIB
    DB    '4'
    DB    'Checksum error at location : '
    DW    ATTRIB
    DB    '0'
    DB    '$'
;
MESG11:
    DB    'Load end address   = '
    DB    '$'
;
;
; PROM READ SEQUENCE
;
;
READ2:
    CALL    CRLF
    LXI    H,MESG6        ;READY TO READ MESSAGE
    CALL    PTXT
    CALL    YORN
    JNC     PPG10A        ;NO, THEN PROGRAM
READ0:
    CALL    CRLF
    LXI    H,MESG5        ;MEM START ETC. MESSAGE
    CALL    PTXT
    CALL    SCAN$OP        ;INPUT PARAMETERS
    LDA    NXCHAR
    CPI    '.'
    JZ     READ0
    MVI    A,040H        ;TURN ON PROM VOLTAGE
    OUT    HACTL
    LHLD    OPR1        ;MEM START ADDRESS
    LDED    OPR3        ;PROM START ADDRESS
READ1:
    CALL    PREAD        ;READ A BYTE OF PROM
    MOV    M,A        ;SAVE BYTE IN MEMORY
    CALL    ADCMP        ;INC ADDRESS AND COMPARE
    JNZ    READ1        ;IF NOT END, READ NEXT BYTE
    XRA    A        ;TURN OFF PROM
    OUT    HACTL
    JMP    PPG10A         ;PROGRAM SEQUENCE
;
;
; INC HL & DE THEN COMPARE WITH (IX)
; EXIT WITH ZERO FLAG SET IF EQUAL
;
;
ADCMP:
    INX    D        ;INC PROM ADDRESS
    MOV    A,D
    ANI    00FH        ;MAX PROM ADDR =00FFFH
    MOV    D,A
    INX    H
    PUSH    D
    PUSH    H        ;SAVE HL & DE
    LDED    OPR2        ;GET RAM END ADDRESS
    INX    D
    ANA    A
    CPHL            ;COMPARE
    POP    H
    POP    D
    RET
;
;
; PROGRAMMING SEQUENCE
;
;
PROG:
    MVI    A,40
    OUT    HACTL        ;TURN ON PROM VOLTAGE
    LHLD    OPR1        ;MEM START ADDRESS
    LDED    OPR3        ;PROM START ADDRESS
PROG1:
    CALL    PREAD        ;READ A BYTE FROM PROM
    CPI    0FFH        ;ERASED?
    JNZ    PROG2        ;NO, PRINT ERROR
PROG1A:
    CALL    ADCMP        ;INC ADDRESS & CHECK FOR END
    JNZ    PROG1
    JMP    PROG3        ;ALL OK, PROGRAM PROM
;
PROG2:
    PUSH    H
    LXI    H,MESG13    ;NOT ERASED MESSAGE
    CALL    PTXT
    POP    H
    IN    DATA
    CALL    PRTER        ;PRINT BAD LOCATION
    CALL    ECHO        ;READ CONSOLE
    CPI    '.'        ;ABORT?
    JZ     PROG9
    CPI    'C'        ;CONTINUE?
    JZ     PROG3
    JMP    PROG1A        ;CHECK MORE LOCATIONS
;
PROG2A:
    MVI    A,0
    OUT    HACTL
    JMP    INITIAL
;
PROG3:
    CALL    CRLF
    MVI    B,065H        ;B < NUMBER OF PROGRAMMING  LOOPS
PROG4:
    LHLD    OPR1        ;MEM START ADDRESS
    LDED    OPR3        ;PROM START ADRESS
    DCR    B        ;ADJUST COUNT
    JZ    PROG6
PROG5:
    PUSH    B        ;SAVE COUNT
    CALL    PPROG        ;PROGRAM ONE BYTE
    POP    B
    CALL    CONSTAT
    JZ     PROG5A
    CALL    CONIN
    CPI    '.'
    JZ     PROG9
PROG5A:
    CALL    ADCMP        ;INC ADDRESS & CHECK FOR END
    JNZ    PROG5        ;FINISH THIS LOOP
    JMP    PROG4
;
PROG6:
    MVI    A,0
    OUT    HACTL        ;TURN OFF ALL CONTROL LINES
    MVI    D,20
PROG6A:
    XRA    A
    CALL    DELAY
    DCR    D
    JNZ    PROG6A
    LHLD    OPR1        ;MEM START ADDRESS
    LDED    OPR3        ;PROM START ADDRESS
PROG7:
    CALL    PREAD        ;READ PROM DATA
    CMP    M        ;COMPARE TO MEMORY DATA
    JNZ    PROG8        ;ERROR IF NOT MATCHED
PROG7A:
    CALL    ADCMP        ;INC ADDRESS & CHECK FOR END
    JNZ    PROG7
    JMP    PROG2A        ;EXIT, COMPLETE
;
PROG8:
    PUSH    PSW
    PUSH    H
    LXI    H,MESG14    ;BAD LOCATION MESSAGE
    CALL    PTXT
    POP    H
    CALL    CONSTAT
    JZ     PROG8A
    CALL    CONIN
    CPI    '.'        ;ABORT?
    JZ     PROG9
PROG8A:
    POP    PSW
    CALL    PRTER        ;PRINT THE ERROR MESSAGE
    JMP    PROG7A        ;CHECK MORE LOCATIONS
;
PROG9:
    LXI    H,MESG15    ;ABORTED MESSAGE
    CALL    PTXT
    JMP    PROG2A
;
;
; PULSE ONE PROM LOCATION
;
;
PPROG:
    CALL    PADD        ;LATCH LSB OF ADDRESS
    MOV    A,D
    ANI    00FH        ;MAX ROM ADDRESS =00FFFH
    ORI    080H
    OUT    HACTL
    MOV    A,M        ;FETCH DATA
    OUT    DATA        ;OUTPUT TO PROM
    MOV    A,D
    ORI    0C0H        ;TURN ON PROGRAMING PULSE
    OUT    HACTL
    MVI    A,1
    CALL    DELAY        ;1 MILLISEC DELAY
    MOV    A,D
    ORI    080H
    ANI    087H        ;TURN OFF PROGRAMING PULSE
    OUT    HACTL
    RET
;
DELAY:
    LXI    B,26 * SPEED    ;DELAY COUNT DEPENDS ON PROC SPEED
    PUSH    PSW
DELAY1:
    DCX    B        ;ADJUST INNER COUNT
    MOV    A,B
    ORA    C        ;DONE?
    JNZ    DELAY1         ;NO
    POP    PSW        ;YES
    DCR    A        ;ADJUST OUTER COUNT
    JNZ    DELAY
    RET
;
;
; READ ONE LOCATION OF PROM
;
;
PREAD:
    CALL    PADD        ;LATCH LSB OF ADDRESS
    MOV    A,D
    ANI    7
    OUT    HACTL
    IN    DATA
    RET
;
;
; LATCH LOWER 8 BITS OF PROM ADDRESS
;
;
PADD:
    MOV    A,E
    OUT    LADD
    RET
;
;
; PRINTS ADDRESS, BAD DATA, GOOD DATA
; OF ERROR LOCATION
;
;
PRTER:
    MOV    B,A
    MOV    A,D
    CALL    PACC        ;PRINT MSB OF ADDRESS
    MOV    A,E
    CALL    PACC        ;PRINT LSB
    MVI    C,' '
    CALL    CONOUT
    MOV    A,B
    CALL    PACC        ;PRINT BAD DATA
    MVI    C,' '
    CALL    CONOUT
    MOV    A,M
    CALL    PACC        ;PRINT GOOD DATA
    CALL    CRLF
    RET
;
;
MESG13:
    DW    ATTRIB
    DB    '4'
    DB    'Not Erased'
    DW    ATTRIB
    DB    '0'
    DB    ' : '
    DB    '$'
;
MESG14:
    DW    ATTRIB
    DB    '4'
    DB    'Bad location'
    DW    ATTRIB
    DB    '0'
    DB    ' : '
    DB    '$'
;
MESG15:
    DW    ATTRIB
    DB    '4'
    DB    ' ABORTED '
    DW    ATTRIB
    DB    '0'
    DB    ACR,ALF
    DB    '$'
;
;
; GET A BYTE FROM AN INTEL 'HEX' FORMAT FILE
; AND RETURN WITH IT IN BINARY FORM IN A
;
;
HEXBIN:
    CALL    BUFFR        ;GET AN ASCII BYTE
    CALL    ASBIN        ;MAKE IT BINARY
    RLC
    RLC
    RLC
    RLC
    PUSH    B
    MOV    C,A
    CALL    BUFFR
    CALL    ASBIN
    ORA    C
    POP    B
    PUSH    PSW
    ADD    C
    MOV    C,A
    POP    PSW
    RET
;
;
; ASCII TO BINARY CONVERSION
;
;
ASBIN:
    SUI    '0'
    CPI    10
    RM
    SUI    007H
    RET
;
;
; UTILITY PRINT ROUTINES
;
;
PASP:
    PUSH    B
    CALL    PACC
    CALL    SPACE
    CALL    CRLF
    POP    B
    RET
;
CRLF:
    MVI    C,ACR
    CALL    CONOUT
    MVI    C,ALF
    JMP    CONOUT
;
SPACE:
    MVI    C,' '
    JMP    CONOUT
;
PTXT:
    MOV    A,M        ;FETCH A BYTE
    CPI    '$'
    RZ
    MOV    C,A
    CALL    CONOUT
    INX    H
    JMP    PTXT
;
PACC:
    PUSH    PSW
    RRC
    RRC
    RRC
    RRC
    CALL    PRVAL
    POP    PSW
PRVAL:
    ANI    00FH
    ADI    090H
    DAA
    ACI    040H
    DAA
    MOV    C,A
    JMP    CONOUT
;
;
; CHECK FOR VALID ASCII 'HEX' CHARACTER
;
;
AORN:
    CPI    '0'
    JC     AORN2
    CPI    '9'+1
    JC     AORN1
    CPI    'A'-1
    JC     AORN2
    CPI    'F'+1
    JNC     AORN2
AORN1:
    XRA    A
    RET
;
AORN2:
    XRA    A
    INR    A
    RET
;
;
; CHECK FOR ENTRY TERMINATOR:
;
; SPACE, COMMA OR CARRIAGE RETURN
;
;
TERMCHK:
    CPI    ' '
    RZ
    CPI    ','
    RZ
    CPI    '.'
    JZ     TCHK0
    CPI    00DH
    RNZ
TCHK0:
    PUSH    B
    CALL    CRLF
    POP    B
    XRA    A
    RET
;
;
; SCAN FOR OPERAND FROM CONSOLE
;
; EXIT WITH DATA IN HL, TERMINATOR
; IN C. IF VALID DATA, RETURN WITH
; ZERO FLAG SET. B CONTAINS NUMBER
; OF CHARACTERS ENTERED
;
;
KEYIN:
    LXI    H,0
    MOV    B,L
KEY1:
    CALL    ECHO
    INR    B        ;INC CHARACTER COUNT
    CALL    TERMCHK        ;TERMINATOR?
    RZ
    CALL    AORN        ;CHECK FOR VALID DATA
    RNZ
    MOV    A,C
    CALL    ASBIN        ;CONVERT TO BINARY
    DAD    H
    DAD    H
    DAD    H
    DAD    H        ;SHIFT 4 BITS
    ADD    L
    MOV    L,A
    JMP    KEY1
;
ECHO:
    JMP    CONIN         ;CP/M DOES ITS OWN ECHO
;
INVCMD:
    MVI    C,'?'
    CALL    CONOUT
    MVI    A,'.'
    STA    NXCHAR
    RET
;
SCAN$OP:
    XRA    A        ;INITIALISE
    STA    OPCNT
    LXI    H,OPR1        ;CLEAR OPERANDS
    SHLD    OP$POINT$
    MOV    M,A        ;RESET HL
    LXI    B,9
    LXI    D,OPRS+1
SCLOOP:
    MOV    A,M        ;GET A BYTE
    STAX    D        ;PUT A BYTE
    INX    H        ;BUMP POINTERS
    INX    D
    DCX    B        ;ADJUST COUNT
    MOV    A,B
    ORA    C        ;DONE?
    JNZ    SCLOOP        ;NO
SCAN1:
    CALL    KEYIN        ;GET 1 OPERAND FROM CONSOLE
    JNZ     INVCMD
    MOV    A,C
    STA    NXCHAR
    CPI    ' '
    JZ     SCAN2
    CPI    ','
    JZ     SCAN2
    DCR    B
    RZ            ;RETURN IF NO DATA
SCAN2:
    PUSH    D        ;PRESERVE CONTENTS OF D
    XCHG            ;DE < DATA
    LHLD    OP$POINT    ;GET POINTER
    MOV    M,E        ;PUT LOW BYTE
    INX    H
    MOV    M,D        ;PUT HIGH BYTE
    INX    H
    SHLD    OP$POINT    ;STORE POINTER
    POP    D
    LDA    OPCNT
    INR    A        ;BUMP OPERAND COUNT
    STA    OPCNT
    MOV    A,C
    CPI    ' '
    JZ     SCAN1
    CPI    ','
    JZ     SCAN1
    RET
;
BUFFR:
    PUSH    H        ;SAVE,
    PUSH    D        ;THE,
    PUSH    B        ;ENVIRONMENT
    LDA    BUFCNT        ;GET POS OF LAST BYTE
                ;READ FROM BUFFER
    CPI    080H        ;AT END OF THE RECORD?
    JNZ    BUFFR1        ;NO, GET NEXT BYTE
    MVI    C,20        ;READ NEXT FILE RECORD
    LXI    D,FCB        ;FCB ADDRESS
    CALL    BDOS
    ORA    A        ;SUCESSFUL READ?
    JNZ    ERROR        ;NO, FINALISE THEN EXIT
    XRA    A        ;YES, RESET A
BUFFR1:
    LXI    H,00080H    ;START OF DISK BUFFER
    MOV    E,A        ;GET OFFSET TO LAST BYTE
                ;READ FROM BUFFER
    INR    A        ;BUMP TO NEXT BYTE
    STA    BUFCNT        ;SAVE NEW LOCATION
    MVI    D,0        ;RESET DE
    DAD    D        ;FORM ACTUAL ADDRESS
    MOV    A,M        ;GET BYTE
    POP    B        ;RESTORE
    POP    D        ; THE
    POP    H        ; ENVIRONMENT
    RET
;
ERROR:
    POP    B
    POP    D
    POP    H
    LXI    H,MESG8        ;READ PAST EOF MESSAGE
    CALL    PTXT
    JMP    EXIT
;
COUNT:    DW    0
OFFSET:    DB    0
OPCNT:    DB    0
NXCHAR:    DB    0
OPENFL:    DB    0
BUFCNT:    DB    0
LDPOINT    DW    0
OP$POINT DW    0
OPRS:    DS    6
OPR1    EQU    OPRS
OPR2    EQU    OPRS+2
OPR3    EQU    OPRS+4
SPVAL    EQU    OPRS+100H
;
    END