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STM32F20xxx Functional overview
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3.4 Embedded Flash memory
The STM32F20x devices embed a 128-bit wide Flash memory of 128 Kbytes, 256 Kbytes,
512 Kbytes, 768 Kbytes or 1 Mbytes available for storing programs and data.
The devices also feature 512 bytes of OTP memory that can be used to store critical user
data such as Ethernet MAC addresses or cryptographic keys.
3.5 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.
3.6 Embedded SRAM
All STM32F20x products embed:
• Up to 128 Kbytes of system SRAM accessed (read/write) at CPU clock speed with 0
wait states
• 4 Kbytes of backup SRAM.
The content of this area is protected against possible unwanted write accesses, and is
retained in Standby or V
BAT mode.
3.7 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.