AN3077 datasheet(35/82 Pages) STMICROELECTRONICS

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AN3077

Functional safety requirements for application software

3.14.1.1

Software test implementation

●

CTU_HWSWTEST_TRIGGERNUM

If the reload signal occurs before all the triggers are generated, an overrun indication is

flagged and the application software must handle the error indication.

Note:

Rationale: Tests if all the triggers configured within a control period have been generated

and serviced.

Note:

Implementation hint: The Cross Triggering Unit Error Flag register (CTUEFR) shows

information about the overrun status.

●

CTU_SWTEST_TRIGGERTIME

Application software must configure one eTimer channel to capture the time at which

each trigger event occurs.

In triggered mode, the time instant of each trigger within one control period is captured

and stored in a FIFO. Application software has to check the FIFO values against the

expected ones according to CTU configuration.

In sequential mode, one eTimer channel is needed to check the correct time of a single

trigger with respect to the corresponding event.

Note:

Rationale: To verify if triggers are generated at the correct time

Note:

Implementation hint: Some eTimer inputs are internally connected to the CTU output.

eTIMER_2 input/outputs are not connected to pins on LQFP144 package. Use eTIMER_2

channels for implementing this safety function to keep the channels from eTIMER_0 or

eTIMER_1 units for functions using port pins (See “Enhanced Motor Control Timer (eTimer)”

in the Device_Number Reference Manual for details).

Note:

Implementation hint: eTimer capture register implements a two entry FIFO, but in CTU

triggered mode up to 8 time values need to be stored. To avoid FIFO overflow condition,

eTimer can be configured to trigger a eDMA transfer to move the captured value to specific

RAM location.

●

CTU_HWSWTEST_TRIGGEROVERRUN

This hardware mechanism checks if a new trigger occurs that requires an action by a

subunit that is currently busy. In this case, an overrun interrupt is generated and the

application software must handle the error condition.

Over-run detection mechanism shall be enabled by software during CTU configuration.

Note:

Rationale: Checks if a new trigger occurs that requires an action by a subunit (such as ADC

command generator) which is currently busy.

Note:

Implementation hint: To enable the over-run detection the IEE flag in the Cross Triggering

Unit Interrupt/eDMA register (CTUIR) register shall be asserted. This interrupt is shared

between several sources of error. The user can discriminate among them by reading the

CTUEFR register.

●

CTU_HWSWTEST_ADCCOMMAND

The CTU stores in its internal FIFOs both the value provided by each ADC conversion

and the channel number. Application software must check the ADC channel number

sequence against what is expected for each FIFO. Moreover, invalid commands issued

by the CTU are flagged and the corresponding error must be handled by the

application software.

Note:

Rationale: To detect if the incorrect channel has been acquired, or if the incorrect ADC

result FIFO is selected

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