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A Collection of Useful Assembly Language Routines
Here is a growing collection of small but useful Z80, 8080 and 8086 Assembly Language routines I use time and time again in programs.  Other donations will be gratefully received.

; BDOS EQUATES for running these routines under CPM ; RDCON       EQU   1     ;CP/M Read character WRCON       EQU   2     ;CP/M Write character PRINT       EQU   9     ;CP/M Print string BDOS        EQU   5 ESC         EQU   1BH CR          EQU   0DH LF          EQU   0AH

 

; Main consol output routine using CPM. ; Character to be sent in [C]. ; All registers unchanged   ZCO:  PUSH  AF       PUSH  BC       PUSH  DE       LD    E,C       LD    C,WRCON       CALL  BDOS       POP   DE       POP   BC       POP   AF       RET To Download Text Click Here

; Main consol input routine using CPM. ; Character returned in [A]. ; All registers (except [A]) unchanged   ZCI:  PUSH  BC       PUSH  DE       LD    C,RDCON       CALL  BDOS       POP   DE       POP   BC       RET To Download Text Click Here

; DISPLAY BIT PATTERN IN [A]  (ZILOG) ; All registers unchanged ; The output will look like:- (10100110)   ZBITS:PUSH  AF       PUSH  BC       PUSH  DE       PUSH  AF       LD    C,' '       CALL  ZCO       LD    C,'('       CALL  ZCO       POP   AF       LD    E,A               LD    B,8 BQ2:  SLA   E           LD    A,18H       ADC   A,A       LD    C,A       CALL  ZCO       DJNZ  BQ2       LD    C,')'       CALL  ZCO       POP   DE       POP   BC       POP   AF       RET To Download Text Click  Here

; Return with 2 HEX digits in [A] from keyboard ; If abort, Carry flag set & ESC is returned in [A] ; All registers unchanged except [A]    (INTEL)   GETHEX:       PUSH  B       MVI   C,RDCON       CALL  BDOS        ;Get a character from keyboard & ECHO                 CPI   ESC       JZ    HEXABORT       CPI   '/'         ;check 0-9, A-F       JC    HEXABORT       CPI   '9'+1       JNC   HEXABORT       CALL  ASBIN       ;Convert to binary       RLC               ;Shift to high nibble       RLC       RLC       RLC       MOV   B,A         ;Store it       PUSH  B       MOV   C,RDCON       CALL  BDOS        ;Get 2nd character from keyboard & ECHO       POP   B                 CPI   ESC       JZ    HEXABORT       CPI   '/'         ;check 0-9, A-F       JC    HEXABORT       CPI   '9'+1       JNC   HEXABORT       CALL  ASBIN       ;Convert to binary       ORA   B           ;add in the first digit       ORA   A           ;To return NC       POP   B       RET ; HEXABORT:       STC               ;Set Carry flag       MVI   A,ESC       POP   B       RET ;                       ;Convert LC to UC UPPER:CPI   'a'         ;must be >= lowercase a       RC                ; else go back...       CPI   'z'+1       ;must be <= lowercase z       RNC               ; else go back...       SUI   'a'-'A'           ;subtract lowercase bias       RET ;                       ASBIN:SUI   30H          ;ASCII TO BINARY CONVERSION ROUTINE       CPI   0AH       RM       SUI   07H       RET     To Download Text Click  Here

; DISPLAY CURRNT VALUE IN [A] (ZILOG) ; All registers unchanged   LBYTE:PUSH  AF       PUSH  BC       PUSH  AF       RRCA       RRCA       RRCA       RRCA       CALL  CONV       CALL  ZCO        POP   AF SF598:CALL  CONV       CALL  ZCO   ;Send to consol       POP   BC       POP   AF       RET ; CONV: AND   0FH   ;CONVERT HEX TO ASCII       ADD   A,90H       DAA       ADC   A,40H       DAA       LD    C,A       RET To Download Text Click  Here

; DISPLAY CURRNT VALUE IN [A] (INTEL) ; All registers unchanged   LBYTE:PUSH  PSW         PUSH  B       PUSH  PSW       RRC       RRC       RRC       RRC       CALL  ZCONV       POP   PSW       CALL  ZCONV       MVI   C,' '       CALL  ZCO       POP   B       POP   PSW       RET ; ZCONV:ANI   0FH   ;HEX to ASCII and print it       ADI   90H       DAA       ACI   40H       DAA       MOV   C,A       CALL  ZCO       RET To Download Text Click  Here

; Return with 2 HEX digits in [A] from keyboard ; If abort, Carry flag set & ESC is returned in [A] ; All registers unchanged except [A]    (ZILOG)   GETHEX:       PUSH  BC       LD    C,RDCON                       CALL  BDOS        ;Get a character from keyboard & ECHO       CALL  UPPER       CP    A,ESC       JR    Z,HEXABORT       CP    '/'         ;check 0-9, A-F       JR    C,HEXABORT       CP    'F'+1       JR    NC,HEXABORT       CALL  ASBIN       ;Convert to binary       SLA   A       SLA   A       SLA   A       SLA   A           ;Shift to high nibble         LD    B,A         ;Store it       PUSH  BC          ;Because CP/M destroys BC       LD    C,RDCON                       CALL  BDOS        ;Get a character from keyboard & ECHO       POP   BC       CALL  UPPER       CP    A,ESC       JR    Z,HEXABORT       CP    '/'         ;check 0-9, A-F       JR    C,HEXABORT       CP    'F'+1       JR    NC,HEXABORT       CALL  ASBIN       ;Convert to binary       OR    A,B         ;add in the first digit       OR    A,A         ;To return NC       POP   BC       RET ; HEXABORT:       SCF               ;Set Carry flag       LD    A,ESC       POP   BC       RET ; ASBIN:SUB   30H   ; ASCII TO BINARY CONVERSION ROUTINE       CP    0AH       RET   M       SUB   07H       RET ; UPPER:CP    A,'a'       RET   C       CP    A,'z'+1       RET   NC       SUB   A,'a'-'A'       RET To Download Text Click  Here

; Binary to ASCII Decimal String Conversion Print Routine ; [DE] contains binary number to be displayed as a decimal number. ; Note String is built right->left in buffer ; Then printed out via CPM.         (ZILOG) ; PRINT_DEC:       LD    HL,BUFFER   ;Location to hold string       LD    (BUFPTR),HL ;Save buffer pointer       EX    DE,HL       LD    A,0       LD    (CURLEN),A  ;Current length of buffer is 0       LD    A,H       LD    (NGFLAG),A  ;Save Sign Value       OR    A           ;Set FLAGS Value       JP    P,CNVERT    ;JMP IF VALYE IS +       EX    DE,HL       LD    HL,0       OR    A           ;CLEAR Carry       SBC   HL,DE                         ;Convert Value to a String CNVERT:           LD    E,0         ;HL := HL DIV 10,  DE := HL MOD 10                                      LD    B,16       OR    A DVLOOP:           RL    L           ;Do a 24-bit shift left       RL    H       RL    E       LD    A,E       SUB   10          ;If remainder is 10 or more next 1       CCF       JR    NC,DECCNT       LD    E,A DECCNT:           DJNZ  DVLOOP       ;continue until all bits are done       RL    L       RL    H CHINS:LD    A,E         ;Insert next character into buffer       ADD   A,'0'       CALL  INSERT       LD    A,H       OR    L       JR    NZ,CNVERT       EXIT: LD    A,(NGFLAG)  ;All done       OR    A           ;Check it + or - overall       JP    P,POS       LD    A,'-'       CALL  INSERT POS:  LD    HL,BUFFER       LD    A,(HL)      ;number of characters in buffer       INC   A       LD    C,A       LD    B,0       ADD   HL,BC       ;Point to end of buffer       LD    (HL),'$'    ;Put in terminating character for CPM       LD    DE,BUFFER+1 ;Now print the complete string       LD    C,PRINT     ;(+1, because buffer count is in first posttion)       CALL  BDOS       RET   INSERT:     PUSH  HL     ;Save for now       PUSH  AF       LD    HL,(BUFPTR) ;Current end of buffer       LD    D,H       LD    E,L       INC   DE          ;DE = End+1       LD    (BUFPTR),DE       LD    A,(CURLEN)       OR    A       JR    Z,EXITMR       LD    C,A       LD    B,0       LDDR              ;Move entire buffer up one byte EXITMR:           LD    A,(CURLEN)       INC   A       LD    (CURLEN),A       LD    (HL),A       EX    DE,HL       POP   AF       LD    (HL),A       POP   HL       RET   BUFPTR:     DS    2           ;pointer to last character in buffer CURLEN:     DS    1           ;Current length NGFLAG:     DS    1 BUFFER:     DB    '           $'    ;<<<<< Decimal string will be built here To Download Text Click  Here

; Do a hexdump of the data in that is in a 512 byte (typically a BIOS DMA) buffer ; [HL] points to the buffer. Change values for [DE] below for different size buffers ; No registers modified    (INTEL)     HEXDUMP:       PUSH  PSW         ;Save everything       PUSH  D       PUSH  H       CALL  CRLF        ;CR/LF first         MVI   D,32        ;print 32 lines       MVI   E,16        ;16 characters across       PUSH  D       PUSH  H           ;Save the buffer location ; SF172:CALL  ZCRLF SF175:CALL  BLANK       MOV   A,M       CALL  LBYTE       ;Display A on CRT/LCD       INX   H       DCR   E       JNZ   SF175       MVI   E,16       DCR   D       JNZ   SF172 ;       CALL  ZCRLF       POP   H           ;Get buffer address again       POP   D           ;Get chars/line again ; XF172:CALL  ZCRLF       ;Now show as ascii XF175:CALL  BLANK       ;send a space character       MOV   A,M       ANI   7FH       CPI   ' '         ;FILTER OUT CONTROL CHARACTERS       JNC   XT33 XT22: MVI   A,'.' XT33: CPI   07CH       JNC   XT22       MOV   C,A         ;SET UP TO SEND       CALL  ZCO       INX   H       DCR   E       JNZ   XF175       MVI   E,16       DCR   D       JNZ   XF172       CALL  ZCRLF        POP   H        POP   D        POP   B       POP   PSW       RET ; BLANK:MVI   C,' '       CALL  ZCO       RET ; ZCRLF:MVI   C,CR       CALL  ZCO       MVI   C,LF       CALL  ZCO       RET To Download Text Click Here