Table of Contents
Advertisement
33.3.2.2 32-bit CRC
To compute a 32-bit CRC:
1. Set CRC_CTRL[TCRC] to enable 32-bit CRC mode.
2. Program the transpose and complement options in the CTRL register as required for
the CRC calculation. See
3. Write a 32-bit polynomial to CRC_GPOLY[HIGH:LOW].
4. Set CRC_CTRL[WAS] to program the seed value.
5. Write a 32-bit seed to CRC_DATA[HU:HL:LU:LL].
6. Clear CRC_CTRL[WAS] to start writing data values.
7. Write data values into CRC_DATA[HU:HL:LU:LL]. A CRC is computed on every
data value write, and the intermediate CRC result is stored back into
CRC_DATA[HU:HL:LU:LL].
8. When all values have been written, read the final CRC result from
CRC_DATA[HU:HL:LU:LL]. The CRC is calculated bytewise, and two clocks are
required to complete one CRC calculation.
Transpose and complement operations are performed on the fly while reading or writing
values. See
Transpose feature
33.3.3 Transpose feature
By default, the transpose feature is not enabled. However, some CRC standards require
the input data and/or the final checksum to be transposed. The user software has the
option to configure each transpose operation separately, as desired by the CRC standard.
The data is transposed on the fly while being read or written.
Some protocols use little endian format for the data stream to calculate a CRC. In this
case, the transpose feature usefully flips the bits. This transpose option is one of the types
supported by the CRC module.
33.3.3.1 Types of transpose
The CRC module provides several types of transpose functions to flip the bits and/or
bytes, for both writing input data and reading the CRC result, separately using the
CTRL[TOT] or CTRL[TOTR] fields, according to the CRC calculation being used.
The following types of transpose functions are available for writing to and reading from
the CRC data register:
1. CTRL[TOT] or CTRL[TOTR] is 00.
Freescale Semiconductor, Inc.
Transpose feature
and
and
CRC result complement
KV4x Reference Manual, Rev. 2, 02/2015
Preliminary
Chapter 33 Cyclic redundancy check (CRC)
CRC result complement
for details.
for details.
657
Advertisement
Table of Contents
