AN4253 datasheet(13/44 Pages) STMICROELECTRONICS

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AN4253

FCCU block

4.2.1

Code sequence

Reading Critical Faults (CF)

Write command OPR=9 to FCCU_CTRL register

Wait for operation to finish (FCCU.CTRL.OPS = SUCCESS)

Read the FCCU_CF register

Reading Non-Critical Faults (NCF)

Write command OPR=9 to FCCU_CTRL register

Wait for operation to finish (FCCU.CTRL.OPS = SUCCESS)

Read the FCCU_NCF register

4.3

Analyze FCCU faults

In most cases this block will be skipped unless application requires special startup code for

different faults.

4.4

STCU fault analysis

This analysis is recommended as any issue found during the built-in self test can signal a

presence of latent faults.

There are three signals routed from STCU to FCCU unit to report different kind of issues:

It is recommended to monitor all three fault signals and take an appropriate action when any

STCU fault is active.

4.4.1

Code sequence

Test bits b’20 and b’27 in Critical faults

Test bit b’12 in Non-critical faults

If any of the testing bits is ‘1’ > Jump to FCCU Fault handler

Otherwise continue in startup

4.5

Save FCCU faults

It is usually required to keep fault values for later analysis by the application code. This

cannot be done by simply leaving status registers untouched and read them later. The

reason is that any present fault in FCCU status register would prevent successful transition

from SAFE mode to DRUN mode.

•

CF[20]

Critical fault found by xBIST test

•

CF[27]

STCU fault of starting the xBIST tests during the runtime, which leads

to content corruption in the RAM array or in the digital logic

•

NCF[12]

Non-critical fault found by xBIST test

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