NXP Semiconductors freescale K51 Series Reference Manual

30.2.3 CRC Control Register (CRC_CTRL)This register controls the configuration and working of the CRC module. Appropriate bitsmust be set before starting a new CRC calculation. A new CRC calculation is initializedby 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_2008hBit 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 0RTOTTOTR 0FXORWASTCRC 0WReset 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 0CRC_CTRL field descriptionsField Description31–30TOTType of Transpose for WritesThese bits define the transpose configuration of the data written to the CRC data register. Refer to thedescription 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.29–28TOTRType of Transpose for ReadThese bits identify the transpose configuration of the value read from the CRC data register. Refer to thedescription 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.27ReservedThis read-only field is reserved and always has the value zero.26FXORComplement Read of CRC data registerSome CRC protocols require the final checksum to be XORed with 0xFFFFFFFF or 0xFFFF. Assertingthis 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.25WASWrite CRC data register as seedWhen this bit is asserted, a value written to the CRC data register is considered a seed value. When thisbit 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...Chapter 30 Cyclic redundancy check (CRC)K51 Sub-Family Reference Manual, Rev. 6, Nov 2011Freescale Semiconductor, Inc. 697