60.6.8 Power-up Reset

After a power-up reset, the SECUMOD is in Backup mode, but in an unpredictable state.

The Slow Clock oscillator takes about one second to start-up. During that time, the Double Frequency Monitor can return an error to the protection manager. It is also possible that other monitors send alarms to the Protection Unit. However, a Clear command can be performed because the secure memories content is empty.

Care must be taken when writing in BUSRAM4KB or BUREG256b after reset. The user must make sure that no Erase sequence is running, otherwise the write access to BUSRAM4KB or BUREG256b is aborted. It is recommended to wait for the system to be established before accessing BUSRAM4KB or BUREG256b. This can last for at least one or two seconds. The verification is performed by reading SECUMOD_SR. If there is no error for a continuous period (one second, for example), the user can access BUSRAM4KB or BUREG256b. If at least one error is detected, the user has to wait first for the ERASE_DONE flag to rise, and then wait again for at least one slow clock period after reading SECUMOD_SR before writing content in SECUMOD_SCR. At this stage, all status bits should be cleared. The user must then ensure that no error is raised in SECUMOD_SR during the next second, for example.