28.5.4 Security and Safety Analysis and Reports

Several types of checks are performed when the PIT64B is running.

The peripheral clock of the PIT64B is monitored by a specific circuitry to detect abnormal waveforms on the internal clock that may affect the behavior of the PIT64B. Corruption on the triggering edge of the clock or a pulse with a minimum duration may be identified. If the CGD flag is set in the Write Protection Status register (PIT64B_WPSR), an abnormal condition occurred on the peripheral clock. This flag is not set under normal operating conditions.

The internal timer sequence of the PIT64B is also monitored and if an abnormal state is detected, the flag PIT64B_WPSR.SEQE is set. This flag is not set under normal operating conditions.

The software accesses to the PIT64B are monitored and if an incorrect access is performed, the flag PIT64B_WPSR.SWE is set. The type of incorrect/abnormal software access is reported in the PIT64B_WPSR.SWETYP field (see PIT64B Write Protection Status Register for details). For example, writing PIT64B_MR, PIT64B_LSBPR (if PIT64B_MR.SMOD=0), PIT64B_MSBPR (if PIT64B_MR.SMOD=0) when the timer is running (after a START command has been issued) is an error. PIT64B_WPSR.ECLASS is an indicator reporting the criticality of the SWETYP report.

The flags CGD, SEQE, SWE and WPVS are automatically cleared when PIT64B_WPSR is read.

If one of these flags is set, the PIT64B_ISR.SECE flag is set and can trigger an interrupt if the SECE bit, in the Interrupt Mask register (PIT64B_IMR), is ‘1’. SECE is cleared by reading PIT64B_ISR.