Crc Calculation Unit; Crc Introduction; Crc Main Features; Figure 2. Crc Calculation Unit Block Diagram - ST STM32F205 series Reference Manual

RM0033
3

CRC calculation unit

This section applies to the whole STM32F20x and STM32F21x and family, unless otherwise
specified.
3.1

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.
3.2

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 2. CRC calculation unit block diagram

CRC computation (polynomial: 0x4C11DB7)
32-bit (write access)
16 12 11
+ X + X + X + X
Figure 2.
AHB bus
Data register (output)
Data register (input)
RM0033 Rev 8
CRC calculation unit
10 8 7 5 4
+X + X + X + X
32-bit (read access)
2
+ X + X + 1
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