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Cyclic Redundancy Checker (CRC) Unit
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
1239
Figure 29-1. CRC checksum processing flow
The following sections describe each step in the process.
29.3.1
Configuring the context
A context consists of a CRC engine and a dedicated set of registers. The MPC5644A CRC module includes
three contexts.
The configuration step consists of:
•
Selecting the polynomial
•
Specifying whether a swap operation is to be performed on the output
•
Specifying whether a bit inversion is to be performed on the output
Selections are made by writing the appropriate values to fields in the CRC_CFG register.
Two standard polynomials are provided by the CRC module: CRC-16-CCITT (x25 protocol) and CRC-32
(ethernet protocol). They are illustrated in
.
Configure Context
Select polynomial, swap, inversion
via the CRC_CFG register
Start
Initialize Seed Value
Write seed value to CRC_CSTAT
register
Write Data to CRC Input
Write 32-bit word, half word or
byte to CRC_INP register
End of
Data Stream
Reached
Read CRC Checksum
Read signature from CRC_OUTP
register
Содержание MPC5644A
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