ARM Technical Support Knowledge Articles

Can ARM11 enter standby mode during debug ?

Applies to: ARM11 processors

Answer

There are a number of conditions which must be met for entry to standby mode:
- Wait for interrupt instruction should be executed
- nETMWFIREADY signal from ETM must be low
- DMA operations should be complete
- Instruction fetches on AHB-I port should be complete
- Data accesses on data/peripheral AHB ports should be complete
- Standby exit condition should be false (this is IRQ/FIQ/EDBGRQ/Halt request)

The gating of the internal clock in standby mode depends on FREEDBGTCKEN signal. If FREEDBGTCKEN
is high, the internal clock will be active during standby to support debug operations.

The standby exit conditions are
- nIRQ interrupt (masked or unmasked)
- nFIQ interrupt (masked or unmasked)
- EDBGRQ external debug request (and debug enabled)
- JTAG Halt request (and debug enabled)

So if you enter debug mode using an external debug request or a JTAG Halt request, this will exit
from standby mode.
You can enter standby mode during debug state by executing a wait for interrupt instruction.

 

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