AN3324 datasheet(12/37 Pages) STMICROELECTRONICS

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AN3324

Module software requirements for non applicative peripherals

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Module software requirements for non applicative

peripherals

This chapter describes the requirements of the software modules that should check the

system peripherals and the Flash. The checks are required for any application.

The peripherals treated in this chapter are accounted as non applicable peripherals

because they are not involved directly in any application Safety Integrity Function (SIF)

please refer to AN3077 (see B.1: Reference documents in Appendix B).

3.1

System Status and Configuration Module (SSCM)

Before executing safety functions, user must perform two actions:

Configure the SSCM to inhibit unintentional execution of the BAM code.

Note:

This requirement is satisfied by asserting the flag PAE in the ERROR register of the SSCM.

Each access to the BAM memory area produces a Prefetch or Abort exception.

Verify that the device operates in Lock-Step Mode (LSM).

Note:

Software needs to check this condition by reading the LSM flag in the System Status

operation.

3.2

Self Test Control Unit (STCU)

After boot, user software must check the STCU to ensure its reliability. The software must

perform several operations based on the STCU status conditions after the power-on self

test. Even if no errors are reported, user software should confirm that the expected and

actual values within the CRC (Cyclic Redundancy Check) and LBIST MISR registers do not

indicate an error.

This software confirmation prevents a fault within the STCU itself incorrectly indicating that

the self test passed.

In the case of no reported errors, user software should confirm that:

The internal CRC computation result matches the expected value.

Note:

Read the CRCE and CRCR registers to check the coherency with the STCU_ERR[CRCS]

flag.

The signature registers of each of the LBIST results match their corresponding

expected values.

Note:

For each LBIST, read the STCU_LBMISREL/H and STCU_LBIST_NMISRRL/H registers to

check the coherency with the STCU_LBS bits.

Read the registers used for Reported Errors and verify that their values are as

expected. Refer to the “Integrity SW operations” section in RM0032 (see B.1:

Reference documents in Appendix B).

Note:

Verify that STCU_LBS, STCU_LBE, STCU_MBSL, STCU_MBEL flag registers values are

as expected. (LBIST and MBIST finished with success).

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