RM0453 Rev 5 525/1450
RM0453 Cyclic redundancy check calculation unit (CRC)
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17 Cyclic redundancy check calculation unit (CRC)
17.1 Introduction
The CRC (cyclic redundancy check) calculation unit is used to get a CRC code from 8-, 16-
or 32-bit data word and a generator polynomial.
Among other applications, CRC-based techniques are used to verify data transmission or
storage integrity. In the scope of the functional safety standards, 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.
17.2 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
• Alternatively, uses fully programmable polynomial with programmable size (7, 8, 16, 32
bits)
• Handles 8-,16-, 32-bit data size
• Programmable CRC initial value
• Single input/output 32-bit data register
• Input buffer to avoid bus stall during calculation
• CRC computation done in 4 AHB clock cycles (HCLK) for the 32-bit data size
• General-purpose 8-bit register (can be used for temporary storage)
• Reversibility option on I/O data
• Accessed through AHB slave peripheral by 32-bit words only, with the exception of
CRC_DR register that can be accessed by words, right-aligned half-words and right-
aligned bytes
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