CRC calculation unit RM0008
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3 CRC calculation unit
Low-density devices are STM32F101xx, STM32F102xx and STM32F103xx
microcontrollers where the Flash memory density ranges between 16 and 32 Kbytes.
Medium-density devices are STM32F101xx, STM32F102xx and STM32F103xx
microcontrollers where the Flash memory density ranges between 64 and 128 Kbytes.
High-density devices are STM32F101xx and STM32F103xx microcontrollers where the
Flash memory density ranges between 256 and 512 Kbytes.
This section applies to the whole STM32F10xxx family, unless otherwise specified.
3.1 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
–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 block diagram is shown in Figure 3.
Figure 3. CRC calculation unit block diagram
AHB bus
32-bit (read access)
Data register (output)
CRC computation (polynomial: 0x4C11DB7)
32-bit (write access)
Data register (input)
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