What are the requirements to meet before applying a Warm reset to a Cortex processor?
Applies to: Cortex processors
When using a Cortex processor, you might want to apply a Warm reset to the processor in certain scenarios, such as debugging or watchdog timeout. ARM recommends that you consider the following points before applying a Warm reset to the processor. Otherwise, the processor might not work properly when out of reset.
- The processor is in a quiescent state.
Otherwise, there might be pending transactions, which can result in unpredictable behaviors. Make sure that the processor is in the (Wait for Interrupt) WFI mode before you apply a Warm reset to the processor.
- The system prevents external events from being sent to the processor.
For example, there are no accesses to the processor from the rest of the system. Interrupts and debug requests are disabled as well.
- The coherency issue, if any, is considered.
For example, before the Warm reset, cache maintenance operations must be explicitly performed by the software to guarantee the coherency. In addition, ARM recommends you to disable the Symmetric Multi-Processing (SMP) mode when using a multi-core processor.
If the above requirements cannot be met, for example when a processor gets hung, you can apply a reset to the subsystem or whole system to revive the processor.
For details about Warm set requirements of a particular processor, refer to the shutdown requirements of the processor in its Technical Reference Manual (TRM).
Contact ARM for more information if you have questions about the Warm reset for a particular processor.
Article last edited on: 2016-02-05 03:19:00
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