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Assembly Source File | 1986-05-08 | 7.4 KB | 259 lines

COMMENT ~ BCD.ASM -- BCD Conversion Routines From `BLUEBOOK of ASSEMBLY ROUTINES for the IBM PC & XT' by Christopher L. Morgan Copyright (C) 1984 by The Waite Group, Inc. >>>>> See BCD.DOC for complete descriptions of routines. <<<<< _____________________________________________________________________________ Contents: --------- BCDIN -- Convert from ASCII Decimal to BCD BCDOUT -- Convert from BCD to ASCII Decimal BCD2I16 -- Convert from BCD to 16-bit Binary I162BCD -- Convert from 16-bit Binary to BCD _____________________________________________________________________________ ~ EXTRN STDIN:FAR,STDOUT:FAR ;_____________________________________________________________________________ ; DATAS SEGMENT PUBLIC BCDBUFF DB 18 DUP(?) DATAS ENDS ;_____________________________________________________________________________ ; CODES SEGMENT PUBLIC BCDIN,BCDOUT,BCD2I16,I162BCD ASSUME CS:CODES,DS:DATAS ;______________________________ BCD ROUTINES _________________________________ ;Routine to convert from ASCII decimal to internal BCD format. ; BCDIN PROC FAR PUSH DS ;Save registers PUSH DI PUSH DX PUSH CX PUSH AX ; ;Set up data segment MOV DX,DATAS ;Point to data segment MOV DS,AX ; ;Clear BCD buffer LEA DI,BCDBUFF ;Point to BCD buffer MOV AL,0 ;zero byte MOV CX,18 ;buffer SIze BCDIN1: MOV [DI],AL ;zero the byte INC DI ;Point to next byte LOOP BCDIN1 BCDIN2: ; ; get the digit CALL STDIN ;Digit comes in AL SUB AL,30H ;Subract 30H JL BCDIN4 ;Check if too low CMP AL,9 JG BCDIN4 ;Check if too high ; ;Multiply buffer by 10 and add new digit LEA DI,BCDBUFF ;Point to BCD buffer MOV CX,18 ;buffer SIze BCDIN3: PUSH CX ;Save counter MOV DL,AL ;Save previous digit MOV AL,[DI] ;Pick up byte from buffer MOV CL,4 ;for a count of 4 SAL AX,CL ;Shift byte left OR AL,DL ;Combine with previous digit MOV [DI],AL ;Result goes back MOV AL,AH ;Prepare for next byte AND AL,0FH ;Strip to byte INC DI ;Point to next byte POP CX ;Restore count LOOP BCDIN3 JMP BCDIN2 BCDIN4: POP AX ;Restore registers POP CX POP DX POP DI POP DS RET ;Return BCDIN ENDP ;------------------------------------------------------------------------------ ;Routine to convert from internal BCD to ASCII decimal ; BCDOUT PROC FAR PUSH DS ;Save registers PUSH SI PUSH DX PUSH CX PUSH AX ; ;Set up data segment MOV AX,DATAS ;Point to data segment MOV DS,AX MOV CX,18 ;for a count of 18 LEA SI,BCDBUFF ;Point ot BCD buffer ADD SI,17 ;Point ot end of BCD buffer MOV DH,0 ;Clear flag for leading zeros BCDOUT1: PUSH CX ;Save loop count MOV AL,[SI] ;get BCD byte DEC SI ;And point to next MOV DL,AL ;Save it ; ;Upper digit MOV CL,4 ;for a count of 4 ROL AL,CL ; rotate byte AND AL,0FH ;just the digit OR DH,AL ;Leading zeros JZ BCDOUT2 ;if so skip digit ADD AL,30H ;make ASCII CALL STDOUT ;Send it out BCDOUT2: POP CX ;Restore count CMP CX,1 ;Last digit ? JNZ BCDOUT3 ;Skip in not MOV DH,0FFH ; set flag if so BCDOUT3: PUSH CX ;Save count MOV AL,DL ;byte back ; ;Lower digit AND AL,0FH ;just the digit OR DH,AL ;Leading zeros ? JZ BCDOUT4 ;if so skip digit ADD AL,30H ;make ASCII CALL STDOUT ;Send it out BCDOUT4: POP CX ;Restore loop count LOOP BCDOUT1 POP AX ;Restore registers POP CX POP DX POP SI POP DS RET ;Return BCDOUT ENDP ;------------------------------------------------------------------------------ ;Routine to convert from internal BCD to internal 16-bit binary. ; BCD2I16 PROC FAR PUSH DS ;Save registers PUSH SI PUSH CX PUSH AX ; ;Set up data segment MOV AX,DATAS ;Point of data segment MOV DS,AX ; ;Set up loop MOV CX,18 ;initialize counter LEA SI,BCDBUFF ;Point to buffer ADD SI,17 ;Point to end of BCD buffer MOV DX,0 ;Set DX to zero BCD2I161: PUSH CX ;Save loop count MOV AL,[SI] ;get BCD byte DEC SI ;And point to next MOV BL,AL ;Save it ; ;Upper digit MOV CL,4 ;for a count of 4 ROL AL,CL ; rotate byte AND AL,0FH ;just the digit CBW PUSH AX ;Save digit MOV AX,DX MOV CX,10 ;multiplier of 10 MUL CX ;multiply MOV DX,AX ;Result in DX POP AX ;Restore digit ADD DX,AX ;Add in digit MOV AL,BL ;byte back ; ;Lower digit AND AL,0FH ;just digit CBW PUSH AX ;Save digit MOV AX,DX MOV CX,10 ;miltiplier of 10 MUL CX ;multiply MOV DX,AX ;Result in DX POP AX ;Restore digit ADD DX,AX ;Add in digit POP CX ;Restore loop count LOOP BCD2I161 POP AX ;Restore registers POP CX POP SI POP DS RET ;Return BCD2I16 ENDP ;----------------------------------------------------------------------------- ;Routine to convert from internal 16-bit binary to internal BCD. ; I162BCD PROC FAR ; ;A binary number is in DX PUSH DS ;Save registers PUSH DI PUSH DX PUSH CX PUSH AX ; ;Set up data segment MOV AX,DATAS ;Point to data segment MOV DS,AX ; ;Clear BCD buffer LEA DI,BCDBUFF ;Point to buffer MOV AL,0 ;zero byte MOV CX,18 ;buffer SIze I162BCD1: MOV [DI],AL ;Clear byte INC DI ;next byte LOOP I162BCD1 ; ;Put the digits in a buffer LEA DI,BCDBUFF ;Point to buffer I162BCD2: MOV AX,DX ;numerator MOV DX,0 ;Clear upper hALf MOV CX,10 ;Divisor of 10 DIV CX ;Divide XCHG AX,DX ;get quotient MOV BL,AL ;Save digit MOV AX,DX ;numerator MOV DX,0 ;Clear upper hALf MOV CX,10 ;Divisor of 10 DIV CX ;Divide XCHG AX,DX ;get quotient MOV CL,4 ;for a count of 4 ROL AL,CL ; rotate digit AND AL,0F0H ;just the digit OR AL,BL ;Combine digits MOV [DI],AL ;Put in buffer INC DI ;next byte CMP DX,0 ;done ? JNZ I162BCD2 POP AX ;Restore registers POP CX POP DX POP DI POP DS RET ;Return I162BCD ENDP ;----------------------------------------------------------------------------- CODES ENDS ; END ;_____________________________________________________________________________ ;>>>>> Physical EOF BCD.ASM <<<<<