mirror of
https://github.com/nathanriggs/AppleIIAsm-Collection.git
synced 2024-11-23 15:32:08 +00:00
96 lines
2.1 KiB
Plaintext
96 lines
2.1 KiB
Plaintext
*
|
|
*``````````````````````````````*
|
|
* DIVD8 :: 8BIT DIVISION (8BR) *
|
|
*- -*
|
|
* DIVIDE ONE 8BIT NUMBER BY *
|
|
* ANOTHER TO GET AN 8BIT *
|
|
* RESULT. UNSIGNED ONLY. *
|
|
* *
|
|
* ORIGINAL AUTHOR IS WHITE *
|
|
* FLAME, AS SHARED ON *
|
|
* CODEBASE64. MINOR CHANGES. *
|
|
*- -*
|
|
* CLOBBERS: *
|
|
* *
|
|
* FLAGS: ????---- REG: AXYM *
|
|
*- -*
|
|
* CYCLES: ??? *
|
|
* SIZE: *
|
|
*- -*
|
|
* USAGE: *
|
|
* *
|
|
* LDA #200 *
|
|
* PHA *
|
|
* PDA #10 *
|
|
* PHA *
|
|
* JSR DIV8 *
|
|
*- -*
|
|
* ENTRY *
|
|
* *
|
|
* LOW BYTE OF RETURN ADDRESS *
|
|
* HIGH BYTE OF RETURN ADDRESS *
|
|
* SECOND NUM TO BE MULTIPLIED *
|
|
* FIRST NUM TO BE MULTIPLIED *
|
|
*- -*
|
|
* EXIT *
|
|
* *
|
|
* .Y = REMAINDER *
|
|
* .X = UNCHANGED *
|
|
* .A = QUOTIENT *
|
|
* *
|
|
* [RETURN] = QUOTIENT *
|
|
* [RETLEN] = 1 (QUOT LENGTH) *
|
|
*,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,*
|
|
*
|
|
DIVD8
|
|
*
|
|
** GET RETURN ADDRESS
|
|
*
|
|
PLA
|
|
STA RETADR
|
|
PLA
|
|
STA RETADR+1
|
|
*
|
|
** GET PARAMETERS
|
|
*
|
|
PLA
|
|
STA :DVEND
|
|
PLA
|
|
STA :DVSOR
|
|
*
|
|
LDA #$00
|
|
LDY #8
|
|
ASL :DVSOR
|
|
:L1 ROL
|
|
CMP :DVEND
|
|
BCC :L2
|
|
SBC :DVEND
|
|
:L2 ROL :DVSOR
|
|
DEY
|
|
BNE :L1
|
|
STA :REM
|
|
*
|
|
** RESTORE RETURN ADDRESS
|
|
*
|
|
LDA RETADR+1
|
|
PHA
|
|
LDA RETADR
|
|
PHA
|
|
*
|
|
** LOAD QUOTIENT INTO A, REMAINDER INTO X
|
|
*
|
|
LDY :REM ; REMAINDER TO Y
|
|
LDA #1
|
|
STA RETLEN
|
|
LDA :DVSOR
|
|
STA RETURN
|
|
*
|
|
RTS
|
|
*
|
|
** DATA
|
|
*
|
|
:REM DS 1
|
|
:DVEND DS 1
|
|
:DVSOR DS 1
|
|
*
|