base:int16_and_uint16_conversion_to_string
Conversion of a number in int16 (lo/hi) into a string in CnvStr.
_ItoA converts a signed number
_UtoA converts an unsigned number
The conversion is obtained via a BCD intermediate value.
bcd = $61 ; system Fac, 3 bytes int16 = $64 ; system Fac, 2 bytes sgn byte 0 CnvStr byte 0,0,0,0,0,0,0 ; 7 bytes: sgn + 5bytes + '\0' CnvTrm byte 0,0,0,0,0,0,0 ;------------------------------- ; Converts a 16bit signed integer into string ;------------------------------- ; by Verz - Jul2019 ;------------------------------- ; ; Call with 16 bit number in int16 ; result in CnvStr ;------------------------------- _ItoA ldy #$0 lda int16+1 ; is it positive? bpl _pos _neg clc ; it's negative: let's 2complement it lda int16 eor #$ff adc #1 sta int16 lda int16+1 eor #$ff adc #0 sta int16+1 ldy #'-' ; prepares the sign value _pos sty sgn jsr _UtoA ; the work is done by _UtoA routine ldy sgn ; if the sign was negative beq _enditoa dex ; adds '-' before the number sta CnvStr,x _enditoa rts ;------------------------------- ; Converts a 16bit unsigned integer into string ;------------------------------- ; by Verz - Jul2019 ;------------------------------- ; ; Call with 16 bit number in int16 ; result in CnvStr ;------------------------------- _UtoA jsr BINBCD16 ; converts the number to BCD ;lda bcd+2 and #$0f ; extracts every byte and adds $30 ora #$30 sta CnvStr+1 lda bcd+1 and #$0f ora #$30 sta CnvStr+3 lda bcd+1 lsr lsr lsr lsr ora #$30 sta CnvStr+2 lda bcd+0 and #$0f ora #$30 sta CnvStr+5 lda bcd+0 lsr lsr lsr lsr ora #$30 sta CnvStr+4 lda #$20 sta CnvStr+0 ;rts ; decomment to avoid stripping leading 0s ldx #1 ; remove 0s at beginning _rem0 lda CnvStr,x cmp #$30 ; if it's a '0' bne _rts lda #$20 ; put a space instead sta CnvStr,x inx cpx #$5 ; exits before last digit bne _rem0 _rts rts ;------------------------------- ; Remove leading spaces from int string ;------------------------------- ; by Verz - Jul2019 ;------------------------------- ; use right after _ItoA or _UtoA ; needs the pos of the first digit in .X ; result in CnvTrm ; if the result is to be in CnvStr then change CnvTrm to CnvStr ;------------------------------- _TrimNum ldy #0 cpx #0 beq _rts _trmlp lda CnvStr,x sta CnvTrm,y ; Change to "sta CnvStr,y" to put the trimmed string in CnvStr beq _rts inx iny jmp _trmlp ;------------------------------- ; Converts a 16bit number to BCD ;------------------------------- BINBCD16 SED ; Switch to decimal mode 2 LDA #0 ; Ensure the result is clear 2 STA bcd+0; 3 STA bcd+1; 3 STA bcd+2; 3 13 CBIT1 ASL int16 ; Shift out one bit 5 ROL int16+1 ; 5 ; LDA bcd+0 ; ADC bcd+0 ; And add into result 3 STA bcd+0 ; 3 ASL int16 ; 5 ROL int16+1 ; 5 ADC bcd+0 ; 3 STA bcd+0 ; 3 ASL int16 ; 5 ROL int16+1 ; 5 ADC bcd+0 ; 3 STA bcd+0 ; 3 ASL int16 ; 5 ROL int16+1 ; 5 ADC bcd+0 ; 3 STA bcd+0 ; 3 ASL int16 ; 5 ROL int16+1 ; 5 ADC bcd+0 ; 3 STA bcd+0 ; 3 ASL int16 ; 5 ROL int16+1 ; 5 ADC bcd+0 ; 3 STA bcd+0 ; 3 96 LDX #7; 2 2 CBIT7 ASL int16 ; Shift out one bit 5 ROL int16+1 ; 5 LDA bcd+0 ; And add into result 3 ADC bcd+0 ; 3 STA bcd+0 ; 3 LDA bcd+1 ; propagating any carry 3 ADC bcd+1 ; 3 STA bcd+1 ; 3 DEX ; And repeat for next bit 2 BNE CBIT7 ; 3 33*7-1=230 LDX #3; 2 2 CBIT13 ASL int16 ; Shift out one bit 5 ROL int16+1 ; 5 LDA bcd+0 ; And add into result 3 ADC bcd+0 ; 3 STA bcd+0 ; 3 LDA bcd+1 ; propagating any carry 3 ADC bcd+1 ; 3 STA bcd+1 ; 3 LDA bcd+2 ; ... thru whole result 3 ADC bcd+2 ; 3 STA bcd+2 ; 3 DEX ; And repeat for next bit 2 BNE CBIT13 ; 3 42*3-1=125 CLD ; Back to binary 2 2; tot 470 rts ; All Done.
usage example:
Example lda #$c0 sta int16 lda #$fd sta int16+1 jsr _UtoA ; converts UInt16 to String jsr _trimnum ; trims leading spaces jsr _PrnNum lda #$c0 sta int16 lda #$fd sta int16+1 jsr _ItoA ; converts Int16 to String jsr _trimnum ; trims leading spaces jsr _PrnNum rts _PrnNum ; prints untrimmed string lda #<CnvStr ldy #>CnvStr jsr $ab1e lda #13 jsr $ffd2 ; prints trimmed string lda #<CnvTrm ldy #>CnvTrm jsr $ab1e lda #13 jsr $ffd2 rts
base/int16_and_uint16_conversion_to_string.txt · Last modified: 2019-08-18 09:35 by verz