Crc Functional Description; Crc Block Diagram; Crc Internal Signals; Crc Operation - STMicroelectronics RM0365 Reference Manual

RM0365
6.3

CRC functional description

6.3.1

CRC block diagram

6.3.2

CRC internal signals

Signal name
6.3.3

CRC operation

The CRC calculation unit has a single 32-bit read/write data register (CRC_DR). It is used to
input new data (write access), and holds the result of the previous CRC calculation (read
access).
Each write operation to the data register creates a combination of the previous CRC value
(stored in CRC_DR) and the new one. CRC computation is done on the whole 32-bit data
word or byte by byte depending on the format of the data being written.
The CRC_DR register can be accessed by word, right-aligned half-word and right-aligned
byte. For the other registers only 32-bit access is allowed.
The duration of the computation depends on data width:
• 4 AHB clock cycles for 32-bit
•
2 AHB clock cycles for 16-bit
•
1 AHB clock cycles for 8-bit
An input buffer allows to immediately write a second data without waiting for any wait states
due to the previous CRC calculation.
The data size can be dynamically adjusted to minimize the number of write accesses for a
given number of bytes. For instance, a CRC for 5 bytes can be computed with a word write
followed by a byte write.

Figure 7. CRC calculation unit block diagram

Table 14. CRC internal input/output signals

Signal type
crc_hclk Digital input
DocID025202 Rev 7
Cyclic redundancy check calculation unit (CRC)
Description
AHB clock
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