SYSCON IRQLATENCY addressOffset = 0x170

The IRQLATENCY register is an eight-bit register which specifies the minimum number of cycles (0-255) permitted for the system to respond to an interrupt request. The intent of this register is to allow the user to select a trade-off between interrupt response time and determinism.

Setting this parameter to a very low value (e.g. zero) will guarantee the best possible interrupt performance but will also introduce a significant degree of uncertainty and jitter. Requiring the system to always take a larger number of cycles (whether it needs it or not) will reduce the amount of uncertainty but may not necessarily eliminate it.Theoretically, the ARM Cortex-M0+ core should always be able to service an interrupt request within 15 cycles. However, system factors external to the cpu, such as bus latencies or peripheral response times, can increase the time required to complete a previous instruction before an interrupt can be serviced. Therefore, accurately specifying a minimum number of cycles that will ensure determinism will depend on the application.

The default setting for this register is 0x010.

Table 1. SYSCON registerName = IRQLATENCY addressOffset = 0x170
Bit Symbol Description Reset value
7:0 LATENCY 8-bit latency value 0x010
31:8 - Reserved -