ST92F124 datasheet(409/429 Pages) STMICROELECTRONICS

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ST92F124/F150/F250 - KNOWN LIMITATIONS

KNOWN LIMITATIONS (Cont’d)

13.2 FLASH CORRUPTION WHEN EXITING STOP MODE

Description

Under very specific conditions, the first read per-

formed in flash memory by the core when exiting

stop mode may be corrupted.

Impact on application

As this first read is an opcode, this corruption may

lead to an unpredictable behavior of the applica-

tion.

Workaround

Description

In ST92F124/F150/F250 datasheet, there is a

warning in the WUCTRL register description:

“In order to avoid to execute register write instruc-

tions after a correct STOP bit setting sequence

and before entering the STOP mode, it is manda-

tory to execute 3 NOP instructions after the STOP

bit setting sequence.”

The workaround is to replace these 3 NOPs by the

following assembly code:

RRx is an unused register in the register file.

Implementation

In a C language software, implement the following

code.

Declare a dummy variable in the register file (for

example in RR0 16-bit register)

And replace the actual STOP bit setting sequence

(specified in datasheet):

nop

ldw RRx,0

#pragma register_file

Dummy_16bit_data

volatile unsigned int

Dummy_16bit_data;

spp(WU_PG);

WU_CTLR = WUm_wuit | WUm_id1s | WUm_stop;

WU_CTLR = WUm_wuit | WUm_id1s;

WU_CTLR = WUm_wuit | WUm_id1s | WUm_stop;

asm("nop");

ST92F124 Datasheet(PDF) 409 Page - STMicroelectronics

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