Crc Functional Description; Crc Registers; Data Register (Crc_Dr); Independent Data Register (Crc_Idr) - STMicroelectronics STM32F405 Reference Manual

CRC calculation unit
4.3

CRC functional description

The CRC calculation unit mainly consists of a single 32-bit data register, which:
•
is used as an input register to enter new data in the CRC calculator (when writing into
the register)
•
holds the result of the previous CRC calculation (when reading the register)
Each write operation into the data register creates a combination of the previous CRC value
and the new one (CRC computation is done on the whole 32-bit data word, and not byte per
byte).
The write operation is stalled until the end of the CRC computation, thus allowing back-to-
back write accesses or consecutive write and read accesses.
The CRC calculator can be reset to 0xFFFF FFFF with the RESET control bit in the
CRC_CR register. This operation does not affect the contents of the CRC_IDR register.
4.4

CRC registers

The CRC calculation unit contains two data registers and a control
The CRC registers have to be accessed by words (32 bits).
4.4.1

Data register (CRC_DR)

Address offset: 0x00
Reset value: 0xFFFF FFFF
31 30 29
rw rw rw
15 14 13
rw rw rw
Bits 31:0 Data register bits
4.4.2

Independent data register (CRC_IDR)

Address offset: 0x04
Reset value: 0x0000 0000
31 30 29
15 14 13
114/1731
28 27 26 25
rw rw rw rw
12 11 10 9
rw rw rw rw
Used as an input register when writing new data into the CRC calculator.
Holds the previous CRC calculation result when it is read.
28 27 26 25
12 11 10 9
Reserved
DocID018909 Rev 11
24 23 22 21
DR [31:16]
rw rw rw rw
8 7 6 5
DR [15:0]
rw rw rw rw
24 23 22 21
Reserved
8 7 6 5
rw rw rw
register.The peripheral
20 19 18 17
rw rw rw rw
4 3 2 1
rw rw rw rw
20 19 18 17
4 3 2 1
IDR[7:0]
rw rw rw rw
RM0090
16
rw
0
rw
16
0
rw