K60P100M100SF2RM Datasheet, PDF (757/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 31 Cyclic redundancy check (CRC)
31.2.3 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 the CTRL[WAS] bit 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
0
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
31–30
TOT
Type of Transpose for Writes
Description
These bits define the transpose configuration of the data written to the CRC data register. Refer to the
description of the transpose feature for the available transpose options.
29–28
TOTR
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.
Type of Transpose for Read
These bits identify the transpose configuration of the value read from the CRC data register. Refer to the
description of the transpose feature for the available transpose options.
27
Reserved
26
FXOR
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.
This read-only field is reserved and always has the value zero.
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.
25
WAS
0 No XOR on reading.
1 Invert or complement the read value of the CRC data register.
Write CRC data register as seed
When this bit is asserted, a value written to the CRC data register is considered a seed value. When this
bit is de-asserted, 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.
Table continues on the next page...
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
757