NXP Semiconductors K22F series User Manual

32.3.1 CRC initialization/reinitialization
To enable the CRC calculation, the user must program CRC_CTRL[WAS],
CRC_GPOLY,necessary parameters for transposition and CRC result inversion in the
applicable registers. Asserting CRC_CTRL[WAS] enables the programming of the seed
value into the CRC_DATA register.
After a completed CRC calculation, the module can be reinitialized for a new CRC
computation by reasserting CRC_CTRL[WAS] and programming a new, or previously
used, seed value. All other parameters must be set before programming the seed value
and subsequent data values.
32.3.2
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.
32.3.2.1
16-bit CRC
To compute a 16-bit CRC:
1. Clear CRC_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.
3. Write a 16-bit polynomial to the CRC_GPOLY[LOW] field. The
CRC_GPOLY[HIGH] field is not usable in 16-bit CRC mode.
4. Set CRC_CTRL[WAS] to program the seed value.
5. Write a 16-bit seed to CRC_DATA[LU:LL]. CRC_DATA[HU:HL] are not used.
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[LU:LL].
8. When all values have been written, read the final CRC result from
CRC_DATA[LU:LL].
Transpose and complement operations are performed on the fly while reading or writing
values. See Transpose feature and CRC result complement for details.
Functional description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
746 NXP Semiconductors

NXP Semiconductors K22F series Specifications

General

Brand	NXP Semiconductors
Model	K22F series
Category	Controller
Language	English