AN3307 datasheet(7/37 Pages) STMICROELECTRONICS

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AN3307

Main differences between STM32F packages and their possible modifications

Doc ID 18186 Rev 4

7/37

To prevent this, it is suggested to initialize the concerned RAM space before calling startup

self-test procedure. A simple loop inserted into startup assembly code can solve the

problem and initialize parity system at dedicated RAM area:

Note:

Real content of the registers copied by STMIA instruction doesn’t care because purpose of

this loop is to initialize the parity system. The content of the RAM will be initialized later by

the compiler standard startup procedure anyway. RAM_block_begin and RAM_block_size

constants' setting should correspond with number of data copied by STMIA instruction to

prevent any undefined memory access.

If the initial software March test is performed over a RAM area dedicated for stack, it

destroys the stack content where the return address of the test routine is stored. That is why

the return address must be saved before the test starts and restored back to the stack after

the test finishes. The return address is kept at dedicated register while the test is running.

The store and restore handling depends on compiler implementation and it can differ for

different level of optimization settings. In case of any such change user has to check, how

the return address is saved into stack and perform adequate store and restore of its value

correctly back before return from test is performed and the address is popped out (follow

intrinsic operations at begin and end of STL_FullRamMarchC() routine at

stm32fxxx_STLFullRamMc.c file).

FLASH tests

While IAR compiler can be set to include 32-bit CRC result compatible with

STMicroelectronics hardware directly into code (see IAR documentation) CRC calculation is

not fully supported by KEIL compiler for STM32 microcontrollers yet. That is why the result

provided by STM32's internal CRC generator cannot be used directly for such invariable

; Program starts here after reset

;------------------------------------------------------------------------

Reset_Handler

; Parity system initialization has to be performed here prior to the

;

startup self-test procedure

;------------------------------------------------------------------------

; r0 is used as a pointer to RAM,

; r1 keeps end address of the area

;------------------------------------------------------------------------

;At every step of the loop, the 32-byte block (r2-r9) is copied to RAM

;

starting from address kept at r0, r0 is then increased by 32

; the loop body is performed while r0<r1

LDR

R0, =RAM_block_begin

ADD

R1, R0, #RAM_block_size

RAM_init_loop

STMIA

R0!, {R2-R9}

CMP

R0, R1

BLT

RAM_init_loop

; RAM is initialized now, program can continue by startup self-test

LDR

R0, =STL_StartUp

BLX

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