Re: CCITT CRC16 [CRC-16] Routines

What I use. Pulled and modified from the ether somewhere

Dim CRC As Word ;CRC16 value
Dim CRC_P As Byte ;Data Array pointer
Dim CRC_B As Byte ;Transfer Buffer
Dim CRC_C As Byte ;Counter
Dim SArray[10] as Byte ;Array of data to do CRC on

;Generate CRC
Clear CRC
For CRC_P = 0 To 9
CRC_B = SArray[CRC_P]
Call CRC16
Next CRC_P
'CRC now has CRC-16


; CRC-16 (x^16+x^15+x^2+x^0)
; Input: CRC_B = Data byte for CRC calculation
;************************************************* *******************
CRC16: ;Note:- CRC is a word. CRC =>LowByte, CRCH =>HighByte
Asm
Movlw 8
Movwf CRC_C ;Load bit counter
CRC_Loop:
Movf CRC,W ;Low byte
Xorwf CRC_B,W
Clrc
Rrf CRCH ;High byte
Rrf CRC ;Low byte
Andlw 1
Bz CRC_Skip
Movlw 0xA0
Xorwf CRCH ;High byte
Movlw 0x01
Xorwf CRC ;Low byte
CRC_Skip:
Rrf CRC_B
Decfsz CRC_C
Jump CRC_Loop
EndAsm
Return

See http://www.lammertbies.nl/comm/info/...lculation.html as a good place to check your code working etc