CFA633-RDI-KS datasheet(74/88 Pages) CRYSTAIFONTZ

74 / 88 page

Crystalfontz America, Inc.

Data Sheet Release Date 2012/02/21

www.crystalfontz.com

CFA633-RDI-KS LCD Module (Hardware v2.0 / Firmware s2v1)

February 2012

Page 74

Algorithm 2B: “C” Improved Bit Shift Implementation

This is a simplified algorithm that implements the CRC.

unsigned short get_crc(unsigned char count,unsigned char *ptr)

{

unsigned short

crc;

//Calculated CRC

unsigned char

//Loop count, bits in byte

unsigned char

data;

//Current byte being shifted

crc = 0xFFFF; // Preset to all 1's, prevent loss of leading zeros

while(count--)

{

data = *ptr++;

i = 8;

{

if((crc ^ data) & 0x01)

{

crc >>= 1;

crc ^= 0x8408;

}

else

crc >>= 1;

data >>= 1;

} while(--i != 0);

}

return (~crc);

}

Algorithm 3: “PIC Assembly” Bit Shift Implementation

This routine was graciously donated by one of our customers.

;====================================================================

; Crystalfontz CFA633 PIC CRC Calculation Example

;

; This example calculates the CRC for the hard coded example provided

; in the documentation.

;

; It uses "This is a test. " as input and calculates the proper CRC

; of 0x93FA.

;====================================================================

#include "p16f877.inc"

;====================================================================

; CRC16 equates and storage

;--------------------------------------------------------------------

accuml

equ

40h

; BYTE - CRC result register high byte

accumh

equ

41h

; BYTE - CRC result register high low byte

datareg

equ

42h

; BYTE - data register for shift

equ

43h

; BYTE - bit counter for CRC 16 routine

Zero

equ

44h

; BYTE - storage for string memory read

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