Information

CRC_CTRL field descriptions (continued)

Field Description

0 Writes to the CRC data register are data values.

1 Writes to the CRC data register are seed values.

TCRC

Width of CRC protocol.

0 16-bit CRC protocol.

1 32-bit CRC protocol.

23–0

Reserved

This read-only field is reserved and always has the value zero.

30.3 Functional description

30.3.1 CRC initialization/reinitialization

To enable the CRC calculation, the user must program the WAS, POLYNOMIAL, and

necessary parameters for transpose and CRC result inversion in the applicable registers.

Asserting CTRL[WAS] enables the programming of the seed value into the CRC data

After a completed CRC calculation, reasserting CTRL[WAS] and programming a seed,

whether the value is new or a previously used seed value, reinitialize the CRC module for

a new CRC computation. All other parameters must be set before programming the seed

value and subsequent data values.

30.3.2 CRC calculations

In 16-bit and 32-bit CRC modes, data values can be programmed 8 bits, 16 bits, or 32 bits

at a time, provided all bytes are contiguous. Noncontiguous bytes can lead to an incorrect

CRC computation.

30.3.2.1 16-bit CRC

To compute a 16-bit CRC:

1. Clear CTRL[TCRC] to enable 16-bit CRC mode.

2. Program the transpose and complement options in the CTRL register as required for

the CRC calculation. See Transpose feature and CRC result complement for details.

Functional description

K20 Sub-Family Reference Manual, Rev. 2, Feb 2012

576 Freescale Semiconductor, Inc.