AppleIIAsm-Collection/disks/disk3_math/T.DIVD8

*
*``````````````````````````````*
* 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
*