ARM FIQs

There is a newsgroup comp.sys.arm where the question like this had been asked (and answered) two days ago. It's Message-ID is

Vadim Borshchev

Thanks Vadim

Dejan, ARM by architecture has only 2 interrupt priorities, IRQ, lower priority and FIQ higher priority. Th is achieves simplicity of interrupt systems. However, there has been a significant improvement from ARM, the Vectored Interrupt Controller also called VIC which allows depending on the implementation up to 32 priorities. Assuming there is no VIC, the FIQ will be your higest priority interrupt source. Assingong it makes most sense to exactly one interrupt source. As the FIQ is the highest address vector, you don't even have to identify the interrupt source, as there is only one and you don't have to branch anywhere because there are no additional vectors on higher addresses. In a nutshell, if you only assign one source to the FIQ, it is the fastest way in the ARM architecture to react to an event. hth, Schwob