Crc Calculation Unit; Crc Introduction; Crc Main Features; Crc Functional Description - ST STM32F423 Reference Manual

CRC calculation unit

4 CRC calculation unit
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 way 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 four AHB clock cycles (HCLK)
•
General-purpose 8-bit register (can be used for temporary storage)
The block diagram is shown in
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)
90/1324
32 26 23 22
X + X + X + X

Figure 7. CRC calculation unit block diagram

16 12 11
+ X + X + X + X
Figure 7.
RM0430 Rev 8
10 8 7 5 4
+X + X + X + X
RM0430
2
+ X + X +1