CRC-16-CCITT - Revision history

Jhoger: /* Code */

2011-08-12T21:35:17Z

Code

← Older revision		Revision as of 14:35, 12 August 2011
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	<pre>		<pre>
	; XMODEM/CRC, YMODEM, ZMODEM CRC-16		; XMODEM/CRC, YMODEM, ZMODEM CRC-16
	; Will CRC up to ~~256~~ bytes at a time.		; Will CRC up to 255 bytes at a time.
	; Call multiple times to CRC more than ~~256~~ bytes.		; Call multiple times to CRC more than 255 bytes.
	; Entry:		; Entry:
	; HL contains initial CRC value. Supply zero for initial block		; HL contains initial CRC value. Supply zero for initial block

Jhoger at 06:36, 11 August 2011

2011-08-11T06:36:34Z

← Older revision		Revision as of 23:36, 10 August 2011
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	RET		RET
	</pre>		</pre>

			[[Category:Model T Developer Reference]] [[Category:8085 Subroutine]]

Jhoger: /* Author */

2011-08-11T06:25:34Z

Author

← Older revision		Revision as of 23:25, 10 August 2011
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	== Author ==		== Author ==

	John R. Hogerhuis		John R. Hogerhuis <jhoger@pobox.com><br/>

	Speaker To Machines, Inc.		Speaker To Machines, Inc.

Jhoger: /* Code */

2011-08-11T06:24:18Z

Code

← Older revision		Revision as of 23:24, 10 August 2011
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	This article includes 8085 code to compute this CRC on blocks as large as 256 characters. It can be called multiple times with the prior checksum to extend the CRC over larger blocks.		This article includes 8085 code to compute this CRC on blocks as large as 256 characters. It can be called multiple times with the prior checksum to extend the CRC over larger blocks.

			== Author ==

			John R. Hogerhuis

			Speaker To Machines, Inc.

	== Code ==		== Code ==

Jhoger: New page: == Overview == The CRC-16-CCITT CRC is used in XMODEM/CRC, YMODEM, and ZMODEM. This article includes 8085 code to compute this CRC on blocks as large as 256 characters. It can be called ...

2011-08-11T06:23:09Z

New page: == Overview == The CRC-16-CCITT CRC is used in XMODEM/CRC, YMODEM, and ZMODEM. This article includes 8085 code to compute this CRC on blocks as large as 256 characters. It can be called ...

New page

== Overview ==

The CRC-16-CCITT CRC is used in XMODEM/CRC, YMODEM, and ZMODEM.

This article includes 8085 code to compute this CRC on blocks as large as 256 characters. It can be called multiple times with the prior checksum to extend the CRC over larger blocks.

== Code ==

<pre>
; XMODEM/CRC, YMODEM, ZMODEM CRC-16
; Will CRC up to 256 bytes at a time.
; Call multiple times to CRC more than 256 bytes.
; Entry:
; HL contains initial CRC value. Supply zero for initial block
; DE contains a pointer to the value to CRC
; B contains the number of bytes to CRC.
; nb: B must be non-zero. No checking is performed here.

; Exit:
; HL contains the CRC
; DE points just past the last CRC'ed character
; B is zero
; C is zero
; A, flags are undefined

CALC_CRC16: LDAX D
XRA H
MOV H,A

MVI C,8
FOR_CRC_BIT: DAD H
JNC NEXT_CRC_BIT
MVI A,$10
XRA H
MOV H,A
MVI A,$21
XRA L
MOV L,A

NEXT_CRC_BIT: DCR C
JNZ FOR_CRC_BIT

INX D
DCR B
JNZ CALC_CRC16
RET
</pre>