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Field
Identifies the transpose configuration of the value read from the CRC Data register. See the description of
the transpose feature for the available transpose options.
00
No transposition.
01
Bits in bytes are transposed; bytes are not transposed.
10
Both bits in bytes and bytes are transposed.
11
Only bytes are transposed; no bits in a byte are transposed.
3
This field is reserved.
Reserved
This read-only field is reserved and always has the value 0.
2
Complement Read Of CRC Data Register
FXOR
Some CRC protocols require the final checksum to be XORed with 0xFFFFFFFF or 0xFFFF. Asserting
this bit enables on the fly complementing of read data.
0
No XOR on reading.
1
Invert or complement the read value of the CRC Data register.
1
Write CRC Data Register As Seed
WAS
When asserted, a value written to the CRC data register is considered a seed value. When deasserted, a
value written to the CRC data register is taken as data for CRC computation.
0
Writes to the CRC data register are data values.
1
Writes to the CRC data register are seed values.
0
Width of CRC protocol.
TCRC
0
16-bit CRC protocol.
1
32-bit CRC protocol.
16.4 Functional description
16.4.1 CRC initialization/reinitialization
To enable the CRC calculation, the user must program CRC_CTRL[WAS], CRC_PH1,
CRC_PH0, CRC_PL1 and CRC_PL0,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_DH1, CRC_DH0, CRC_DL1 and
CRC_DL0 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.
NXP Semiconductors
CRC_CTRL field descriptions (continued)
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
Chapter 16 Cyclic redundancy check (CRC)
Description
251
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