S32K11x, SM_211 FTT 100ms

[luca_toso]

Hello, 

according to SM_211 of Safety Manual (Rev.4) , "It is assumed that the Application Fault Tolerant Time Interval is 100 ms."

In our understanding, the implication is that shorter FTTI (t<100ms) can not be guaranteed with this uc - hence the software/application shall have an FTTI > 100ms. 

Is this correct or the implication is that 100ms is the upper limit for the application and safety relevant project shall have a t <100ms FTTI?

Thanks and best regards, 

L

[nxf61080 · Accepted solution]

Hi L,

Please find below the answer:

L: In our understanding, the implication is that shorter FTTI (t<100ms) can not be guaranteed with this uc - hence the software/application shall have an FTTI > 100ms.

MS: The single-point Fault Tolerant Time Interval (FTTI)/Process Safety Time (PST) [Item level] is the time span between a failure that has the potential to give rise to a hazardous event and the time by which counteraction has to be completed to prevent the hazardous event from occurring.

Fault indication time(MCU) is the time from the occurrence of a fault to when the S32K1xx and S32K14xW is switched into a Safe stateMCU.

FTTI is set at item level and not uc level. Fault Indication time is for uc. PFA the image below for better understanding:

L: Is this correct or the implication is that 100ms is the upper limit for the application and safety relevant project shall have a t <100ms FTTI?”

MS: Here FTTI>=100ms. So, 100ms is the lower limit for the application and safety project shall have a t>=100msFTTI.

Thanks and regards,
Manibha Sharma