Datasheet

DocID022152 Rev 8 21/202
STM32F405xx, STM32F407xx Description
2.2.5 CRC (cyclic redundancy check) calculation unit
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 software
signature during runtime, to be compared with a reference signature generated at link-time
and stored at a given memory location.
2.2.6 Embedded SRAM
All STM32F40xxx products embed:
• Up to 192 Kbytes of system SRAM including 64 Kbytes of CCM (core coupled memory)
data RAM
RAM memory is accessed (read/write) at CPU clock speed with 0 wait states.
• 4 Kbytes of backup SRAM
This area is accessible only from the CPU. Its content is protected against possible
unwanted write accesses, and is retained in Standby or V
BAT mode.
2.2.7 Multi-AHB bus matrix
The 32-bit multi-AHB bus matrix interconnects all the masters (CPU, DMAs, Ethernet, USB
HS) and the slaves (Flash memory, RAM, FSMC, AHB and APB peripherals) and ensures a
seamless and efficient operation even when several high-speed peripherals work
simultaneously.
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