nrf51822's original interrupt priority

Question

Hi everyone,
I want to know the original interrupt priority of nrf51822, without using soft device or using NVIC_SetPriority(IRQn_Type IRQn, uint32_t priority). I also want to know whether can I find this priority information through the nrf51822's datasheet or not. Thank you.

Vidar Berg · Accepted Answer

Interrupt handling on the nRF51 series is the same as with other cortex-M0 based controllers. The Cortex-M0 generic user guide does therefore apply to the nRF51 as well. See section 4.2.6 for details about the interrupt priorities. 
 There are 4 programmable interrupts available on all interrupts besides the fixed ones on Reset(-3), NMI(-2) and hardfault(-1). 0 is the highest programmable priority, and 3 is the lowest. Also note that an interrupt is set to the highest priority at startup unless explicitly set with NVIC_NVIC_SetPriority(). 
 Just for reference: the application can use interrupt priorities APP(L) (3) and APPL(H) (1) when a softdevice is enabled. The figure below from S110-SDS chapter 11.2 illustrates what instances that uses the available priorities. Here you can see that the highest programmable priority(0) is used by the lower stack, hence not available to the application.

nrf51822's original interrupt priority

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