Crc Calculation Unit; Crc Introduction; Crc Main Features; Figure 8. Crc Calculation Unit Block Diagram - STMicroelectronics STM32F405 Reference Manual

RM0090
4

CRC calculation unit

This section applies to the whole STM32F4xx family, unless otherwise specified.
4.1

CRC introduction

The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from a 32-bit
data word and a fixed generator polynomial.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the EN/IEC 60335-1 standard, they offer a means of
verifying the Flash memory integrity. The CRC calculation unit helps compute a signature of
the software during runtime, to be compared with a reference signature generated at link-
time and stored at a given memory location.
4.2

CRC main features

•
Uses CRC-32 (Ethernet) polynomial: 0x4C11DB7
–
•
Single input/output 32-bit data register
•
CRC computation done in 4 AHB clock cycles (HCLK)
• General-purpose 8-bit register (can be used for temporary storage)
The block diagram is shown in
32 26 23 22
X + X + X + X

Figure 8. CRC calculation unit block diagram

DocID018909 Rev 11
16 12 11
+ X + X + X + X
Figure 8.
CRC calculation unit
10 8 7 5 4
+X + X + X + X
2
+ X + X +1
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