Changes
CRC16 calculation
''This code is untested and may not work as advertised or at all.''
<pre>
CRC16:
;Borrowed from http://zilog.sh.cvut.cz/~base/misc/z80bits.html
; and moddified to be a loop
;The arrow comments show what lines I added or commented out from the original.
;Inputs: de->data bc=number of bytes
;Outputs: hl=CRC16
push bc ;<---<<<
push de ;<---<<<
push af ;<---<<<
ld hl,$FFFF
push bc ;<---<<<
CRC16_Read:
ld a,(de)
inc de
xor h
ld h,a
ld b,8
CRC16_CrcByte:
add hl,hl
jr nc,CRC16_Next
ld a,h
xor $10
ld h,a
ld a,l
xor $21
ld l,a
CRC16_Next:
djnz CRC16_CrcByte
; dec c ;>>>--->
pop bc ;<---<<<
dec bc ;<---<<<
push bc ;<---<<<
ld a,b ;<---<<<
or c ;<---<<<
jr nz,CRC16_Read
pop bc ;<---<<<
pop af ;<---<<<
pop de ;<---<<<
pop bc ;<---<<<
ret
</pre>
<pre>
CRC16:
;Borrowed from http://zilog.sh.cvut.cz/~base/misc/z80bits.html
; and moddified to be a loop
;The arrow comments show what lines I added or commented out from the original.
;Inputs: de->data bc=number of bytes
;Outputs: hl=CRC16
push bc ;<---<<<
push de ;<---<<<
push af ;<---<<<
ld hl,$FFFF
push bc ;<---<<<
CRC16_Read:
ld a,(de)
inc de
xor h
ld h,a
ld b,8
CRC16_CrcByte:
add hl,hl
jr nc,CRC16_Next
ld a,h
xor $10
ld h,a
ld a,l
xor $21
ld l,a
CRC16_Next:
djnz CRC16_CrcByte
; dec c ;>>>--->
pop bc ;<---<<<
dec bc ;<---<<<
push bc ;<---<<<
ld a,b ;<---<<<
or c ;<---<<<
jr nz,CRC16_Read
pop bc ;<---<<<
pop af ;<---<<<
pop de ;<---<<<
pop bc ;<---<<<
ret
</pre>
