Datasheet

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STM32L072xx Functional overview
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3.8 Memories
The STM32L072xx devices have the following features:
• 20 Kbytes of embedded SRAM accessed (read/write) at CPU clock speed with 0 wait
states. With the enhanced bus matrix, operating the RAM does not lead to any
performance penalty during accesses to the system bus (AHB and APB buses).
• The non-volatile memory is divided into three arrays:
– 64, 128 or 192 Kbytes of embedded Flash program memory
– 6 Kbytes of data EEPROM
– Information block containing 32 user and factory options bytes plus 8 Kbytes of
system memory
Flash program and data EEPROM are divided into two banks. This allows writing in one
bank while running code or reading data from the other bank.
The user options bytes are used to write-protect or read-out protect the memory (with
4 Kbyte granularity) and/or readout-protect the whole memory with the following options:
• Level 0: no protection
• Level 1: memory readout protected.
The Flash memory cannot be read from or written to if either debug features are
connected or boot in RAM is selected
• Level 2: chip readout protected, debug features (Cortex-M0+ serial wire) and boot in
RAM selection disabled (debugline fuse)
The firewall protects parts of code/data from access by the rest of the code that is executed
outside of the protected area. The granularity of the protected code segment or the non-
volatile data segment is 256 bytes (Flash memory or EEPROM) against 64 bytes for the
volatile data segment (RAM).
The whole non-volatile memory embeds the error correction code (ECC) feature.
3.9 Boot modes
At startup, BOOT0 pin and nBOOT1 option bit are used to select one of three boot options:
• Boot from Flash memory
• Boot from System memory
• Boot from embedded RAM
The boot loader is located in System memory. It is used to reprogram the Flash memory by
using USB (PA11, PA12), USART1(PA9, PA10) or USART2(PA2, PA3). See STM32™
microcontroller system memory boot mode AN2606 for details.
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