33 lines
642 B
ArmAsm
33 lines
642 B
ArmAsm
.define Addsub
|
|
.sect .text
|
|
.sect .rom
|
|
.sect .data
|
|
.sect .bss
|
|
.sect .text
|
|
|
|
! This subroutine is used by the fourbyte addition and subtraction
|
|
! routines.
|
|
! It puts the address of the second operand into
|
|
! the zeropage locations ADDR and ADDR+1
|
|
! The address of the first operand is put into
|
|
! zeropage locations ADDR+2 and ADDR+3.
|
|
|
|
|
|
Addsub:
|
|
clc
|
|
lda SP+2
|
|
sta ADDR ! address of second operand (lowbyte)
|
|
adc #4
|
|
sta SP+2
|
|
sta ADDR+2 ! address of first operand (lowbyte)
|
|
lda SP+1
|
|
sta ADDR+1 ! address of second operand (highbyte)
|
|
adc #0
|
|
sta ADDR+3 ! address of first operand (highbyte)
|
|
sta SP+1
|
|
ldy #0
|
|
ldx #0x0FC ! do it 4 times
|
|
rts
|
|
|
|
|