ARM Technical Support Knowledge Articles

Can the ARM7TDMI-S accept asynchronous interrupts?

Applies to: ARM7TDMI-S

Scenario

If the ARM7TDMI-S receives an asynchronous interrupt on nIRQ or nFIQ, will the processor crash and if so, why?

Answer

The ARM7TDMI-S cannot accept asynchronous interrupts; nFIQ and nIRQ must be synchronous inputs and they are sampled on the rising edge of CLK.

The ARM7TDMI-S uses several blocks of logic to handle interrupts. Asynchronous interrupts can cause these internal logic blocks to contain conflicting information about the state of an interrupt.

If the ARM7TDMI-S receives an asynchronous interrupt then the behavior is unpredictable and the processor might 'crash', due to a deadlock occurring, cache corruption, etc.

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