The AXI CDMA interrupt coalescing feature is enabled by setting the CDMACR.IRQThreshold field to a value greater than the default value of 1. When a SG session is started in the CDMA, the CDMACR.IRQThreshold field is loaded into the SG Engine threshold counter. With each Interrupt On Complete event generated by the SG Engine (occurs whenever the AXI CDMA completes a transfer descriptor), the threshold count is decremented. When the count reaches zero, an IOC_Irq is generated by the SG Engine. If the CDMACR.IOC_IrqEn = 1, an interrupt is generated on the AXI CDMA cdma_introut signal.
If the delay interrupt feature is enabled (CDMACR.IRQDelay not equal to 0), a delay interrupt event causes a reload of the SG Engine interrupt threshold counter. In addition, a write by the software application to the threshold value (CDMACR.Threshold), the internal threshold counter is reloaded.