I'm just playing with my MC 68HC11; in C i can perform a simple byte swap by doing something like this:
swapped = ((num>>24)&0xff) | // move byte 3 to byte 0
((num<<8)&0xff0000) | // move byte 1 to byte 2
((num>>8)&0xff00) | // move byte 2 to byte 1
((num<<24)&0xff000000); // byte 0 to byte 3
But now i want to achieve something a little harder using assembly code:
I created an ARRAY and added some values (using little endian logic). I want to read that ARRAY and swap all the values into big endian logic and store them inside "BIGENDIAN". I was thinking something like this:
RWM EQU $0
ROM EQU $C000
RESET EQU $FFFE
ORG RWM
BIGENDIAN RMB 16
ORG ROM
Main:
END BRA END
ARRAY DW $0124,$FEEB,$0011,$0070,$ABEF,$074B,$8004,$8080
ORG RESET
DW Main
I tried but it did not work properly.
DW creates 16-bit words.
(Your C example is for 32-bit words.)
For 16-bit one possibility is this:
RAM equ $0
ROM equ $C000
Vreset equ $FFFE
org RAM
BIGENDIAN rmb 16
org ROM
ARRAY dw $0124,$FEEB,$0011,$0070,$ABEF,$074B,$8004,$8080
Start ldx #ARRAY ;X -> source
ldy #BIGENDIAN ;Y -> destination
Loop ldd ,x ;A = MSB, B = LSB (big endian view)
staa 1,y
stab ,y
; one alternative for above two instructions
; pshb
; tab
; pula
; std ,y
ldab #2 ;B = word size
abx ;X -> next word
aby ;Y -> next word
cpx #ARRAY+::ARRAY
blo Loop
Done bra *
org Vreset
dw Start
If you meant 32-bit words, so two 16-bit should be considered one word, I'll revise.