AN3324 Datasheet, PDF (21/37 Pages) STMicroelectronics – Implementing power-on self tests

AN3324
Module software requirements for non applicative peripherals
3.11
Note:
Note:
Temperature sensors
There are two temperature sensors: temperature sensor 0 mapped to ADC_0 channel 15
and temperature sensor 1 mapped to ADC_1 channel 15.
During power up, user software has to read temperature sensors and verify that the values
are similar as means of assessing the functionality of the sensors.
In case of a fault, software must trigger the appropriate reaction. To set a proper threshold
the customer must consider that the maximum operating junction temperature is 150 °C, for
details please refer to SPC56EL60 datasheet (see B.1: Reference documents in Appendix
B) and the temperature sensor accuracy is 10 °C.
It is mandatory to read the 2 sensors synchronously or with a reduced time interval.
It is important to note that the ADC is part of the temperature measuring safety integrity
function, and it is therefore required that the BIST of the ADC must be executed once after
the boot even if the ADC is not in application use.
3.12
Note:
Caution:
Software Watchdog Timer (SWT)
The SWT has to be enabled and configuration registers have to be hard-locked against
manipulation.
The time window settings of the SWT have to be set to a value less than the PST^(e) (process
safety time). Detection latency is smaller than process safety time.
Before the safety function is executed, the software must verify that the SWT is enabled by
reading the SWT control register (SWT_CR).
To enable the SWT and to hard-lock the configuration register, the WEN and HLK flags of
the SWT control register (SWT_CR) must be asserted. The timeout register (SWT_TO)
must contain a 32-bit value that represents a timeout less than the process safety time.
SWT must be refreshed with a timeline that depends by setted timeout (SWT_TO value).
For this reason it should be configured properly when MCU execute uninterruptible tasks
(see Section 3.10.1: Array integrity self check procedure) to avoid application reset.
e. PST is strictly application dependant.
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