Implementation of the HDLC CRC calculation

Details Implementation of the HDLC CRC calculation Implementation of the HDLC CRC calculation

1993-09-22

1994-06-28

Shaw, Gareth D.

Excavating

371 377, 371 379, G06F 1110

Patent

active

053253728

ABSTRACT:
In accordance with the present invention, a multi-bit CRC character is created by generating a most significant bit (MSB) portion and a least significant bit (LSB) portion in parallel and then combining the MSB and LSB portions to provide the CRC character. This is accomplished by first XORing a multi-bit input character and a current multi-bit CRC high value character stored in a CRC high value latch. The result of this initial XOR operation serves as the input to a high value look-up table which maps the input to a corresponding high value look-up table output character. The value look-up table output character is XORed with a current multi-bit CRC low value character stored in a CRC low value latch to generate an updated CRC high value character. In parallel with the generation of the updated CRC high value character, the result of the initial XOR operation is also provided as the input to a low value look-up table which maps the input to a corresponding updated CRC low value character. The updated CRC high and low value characters are combined to respectively provide the MSB and LSB portions of the CRC character. Both the high value latch and the low value latch are iteratively updated utilizing the updated CRC high and low value characters, respectively. The above-described operation is, thus, performed repetitively on an iteratively updated input character.

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