SOFTWARE MANUAL C32
25 ATTACHMENT D: CRC CALCULATION UNIT
25.1 RELATED DOCUMENTS
The following pages are excepted from the STMicroelectronics reference manual RM0090 for microcontroller memory and
peripherals applying to the whole STM32F4xx family, unless otherwise specified.
Further information is available from STMicroelectronics web site (http://www.st.com):
•
STM32F40x and STM32F41x datasheets
•
STM32F42x and STM32F43x datasheets
•
For information on the Arm® Cortex®-M4 with FPU, refer to the STM32F3xx/F4xxx Cortex®-M4 with FPU
programming manual (PM0214).
25.2 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 linktime and stored at a given memory location.
25.3 CRC MAIN FEATURES
Uses CRC-32 (Ethernet) polynomial: 0x4C11DB7
– X
32
+ X
26
+ X
23
+ X
22
+ X
16
+ X
12
+ X
11
+ X
10
+X
8
+ X
7
+ X
5
+ X
4
+ X
2
+ X + 1
• 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 CRC calculation unit block diagram is shown in figure below
:
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