AN4253 datasheet(19/44 Pages) STMICROELECTRONICS

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AN4253

Safe mode block

6.2.1

Code sequence

Extract the S_CURRENT_MODE bit field

Check if the value is equal to 2 (safe mode)

If Yes > go to mode transition step, otherwise continue with

next startup block

6.3

Mode change to DRUN request

Mode change request consist of a sequence of two 32 bit writes instruction containing

requested mode (3=DRUN) together with a key, where the second key is the inverted value

of the first one.

It is necessary to wait for the end of the transition. Ongoing transition is reported by

MTRANS bit in ME.GS register.

6.3.1

Code sequence

Write value 0x30005AF0 (DRUN + 1.key) to ME.MCTL register

(0xC3FDC004)

Write value 0x3000A50F (DRUN + 2.key) to ME.MCTL register

(0xC3FDC004)

Read ME.GS register

Check MTRANS bit, if ‘1’ > go back to step 3 (Read ME.GS

6.4

DRUN mode check

If there is no pending FCCU fault and FCCU reset flags in the RGM module are cleared,

mode transition should finish successfully. If not, a fault handler must handle this problem.

S_CURRENT_MODE bit field should equal to number 3 (DRUN).

6.4.1

Code sequence

Read ME.GS register

Extract S_CURRENT_MODE bit field

Check if the value equals to 3 (DRUN), if No > go to

ME_Fault_handler

6.5

ME fault handler

ME_Fault_handler shall handle the situation when a requested transition from safe mode to

DRUN mode fails and the microcontroller remains in the safe mode. A reason can be an

unsuccessful clear operation of FCCU faults or the presence of another hardware fault.

AN4253 датащи(PDF) 19 Page - STMicroelectronics