Information
30.2.3 CRC Control register (CRC_CTRL)
This register controls the configuration and working of the CRC module. Appropriate bits
must be set before starting a new CRC calculation. A new CRC calculation is initialized
by asserting CTRL[WAS] and then writing the seed into the CRC data register.
Address: CRC_CTRL is 4003_2000h base + 8h offset = 4003_2008h
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R
TOT
TOTR
0
FXOR
WAS
TCRC
0
W
Reset
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
CRC_CTRL field descriptions
Field Description
31–30
TOT
Type Of Transpose For Writes
Define the transpose configuration of the data written to 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.
29–28
TOTR
Type Of Transpose For Read
Identify 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.
27
Reserved
This read-only field is reserved and always has the value zero.
26
FXOR
Complement Read Of CRC Data Register
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.
25
WAS
Write CRC Data Register As Seed
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.
Table continues on the next page...
Chapter 30 Cyclic Redundancy Check (CRC)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 575