1984-12-17 11:03:13 +00:00
|
|
|
.define Xor
|
1987-01-30 18:41:42 +00:00
|
|
|
.sect .text
|
|
|
|
|
.sect .rom
|
|
|
|
|
.sect .data
|
|
|
|
|
.sect .bss
|
|
|
|
|
.sect .text
|
1984-12-17 11:03:13 +00:00
|
|
|
|
|
|
|
|
! This subroutine performs the exclusive or on two groups of bytes.
|
|
|
|
|
! The groups consists of atmost 254 bytes.
|
|
|
|
|
! The result is on top of the stack.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Xor:
|
|
|
|
|
lda SP+1
|
|
|
|
|
sta ADDR+1 ! address of first group (lowbyte)
|
|
|
|
|
lda SP+2
|
|
|
|
|
sta ADDR ! address of first group (highbyte)
|
|
|
|
|
clc
|
|
|
|
|
tya
|
|
|
|
|
adc SP+2
|
|
|
|
|
sta SP+2 ! new stackpointer (lowbyte)
|
|
|
|
|
sta ADDR+2 ! address of second group (lowbyte)
|
|
|
|
|
lda #0
|
|
|
|
|
adc SP+1
|
|
|
|
|
sta SP+1 ! new stackpointer (highbyte)
|
|
|
|
|
sta ADDR+3 ! address of second group (highbyte)
|
|
|
|
|
1: dey
|
|
|
|
|
lda (ADDR),y ! get byte first group
|
|
|
|
|
eor (ADDR+2),y ! exclusive or with byte second group
|
|
|
|
|
sta (ADDR+2),y ! restore result
|
|
|
|
|
tya
|
|
|
|
|
bne 1b
|
|
|
|
|
rts
|
|
|
|
|
|
|
|
|
|
|
