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AURIX™ MCU: What happens when there is not enough free context? – KBA234980

AURIX™ MCU: What happens when there is not enough free context? – KBA234980

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AURIX™ MCU: What happens when there is not enough free context? – KBA234980

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Not enough free context could be detected by the context management subsystem and result in the Free Context List Depletion (FCD) / Free Context List Underflow (FCU) trap.

FCD occurs when the CSA List Head Pointer register (FCX) points to the free CSA List Limit Pointer (LCX), which is a free element typically chosen close to the last free element of the Context Save Area (CSA) limit. This means that the free context list is ‘almost empty’. The operation responsible for the context save completes normally and then the FCD trap is taken. The FCD trap handler is normally expected to take some form of action to rectify the context list depletion.

FCU, on the other hand, occurs when the FCX = null, meaning that the free context list is empty and the system cannot perform a context switch properly. This means that the architectural state is lost. The occurrence of an FCU trap is a non-recoverable system error, which means that the user should ultimately initiate a system reset.

For more details, see the “Context Management (Trap Class 3)” section of the TriCore™ TC1.6.2 core architecture manual volume 1.

 Note:          This KBA applies to the following series of AURIX™ MCUs:

  • AURIX™ TC2xx series
  • AURIX™ TC3xx series

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