34 lines
801 B
ArmAsm
34 lines
801 B
ArmAsm
|
.define Exg
|
||
|
|
|
||
|
|
! This subroutine exchanges two groups of bytes on the top of the
|
||
|
|
! stack. The groups may consist of atmost 255 bytes.
|
||
|
|
! This number is in register Y.
|
||
|
|
! The exchange is from ADDR, ADDR+1 to ADDR+2, ADDR+3
|
||
|
|
|
||
|
|
|
||
|
|
Exg:
|
||
|
|
lda SP+1
|
||
|
|
ldx SP+2
|
||
|
|
stx ADDR ! address of first group (lowbyte)
|
||
|
|
sta ADDR+1 ! address of first group (highbyte)
|
||
|
|
sty Ytmp ! save number of bytes to be exchanged
|
||
|
|
clc
|
||
|
|
lda SP+2
|
||
|
|
adc Ytmp
|
||
|
|
sta ADDR+2 ! address of second group (lowbyte)
|
||
|
|
lda SP+1
|
||
|
|
adc #0
|
||
|
|
sta ADDR+3 ! address of second group (highbyte)
|
||
|
|
1: dey
|
||
|
|
lda (ADDR),y ! get byte from first group
|
||
|
|
pha ! temporary save
|
||
|
|
lda (ADDR+2),y ! get byte from second group
|
||
|
|
sta (ADDR),y ! store in first group
|
||
|
|
pla ! get temporary saved byte
|
||
|
|
sta (ADDR+2),y ! store in second group
|
||
|
|
tya
|
||
|
|
bne 1b ! perform n times
|
||
|
|
rts
|
||
|
|
|
||
|
|
|