RX610 Group
10. ICU
R01UH0032EJ0120 Rev.1.20
Page 248 of 1006
Feb 20, 2013
10.4.4
Determining Priority
The interrupt control unit determines interrupt priority for each interrupt destination.
If multiple interrupt requests are generated for the same destination, the interrupt from the highest priority source is
accepted. The method used to determine the priority depends on the interrupt request destination.
(1)
Determining Priority when Interrupt Request Destination is CPU
For a group for which the ISEL[1:0] bits in ISELRi are set to 00b, the interrupt source with the larger value of the
interrupt priority level select bits IPR[2:0] in IPRi takes precedence. If multiple interrupt sources that have the same
priority level (same values of the IPR[2:0] bits in IPRi) are generated, the interrupt source with the smallest vector
number takes precedence.
When an interrupt source specified as the fast interrupt (described in a later section) is generated, the interrupt request is
conveyed to the CPU as an interrupt with the highest priority level (7), regardless of the value of the corresponding
IPR[2:0] bits in IPRi and vector number.
(2)
Determining Priority when the DTC is the Destination of the Interrupt Request
The IPR[2:0] bits in IPRi have no effect on a group for which 01b is set in the ISEL[1:0] bits in ISELRi. An interrupt
source with a smaller vector number takes precedence.
(3)
Determining Priority when the DMAC is the Destination of the Interrupt Request
For a group for which 10b or 11b is set in the ISEL[1:0] bits in ISELRi, the IPR[2:0] bits in IPRi have no effect. The
interrupt priority is determined by the setting of the DMAC. See section 12, DMA Controller (DMAC).
10.4.5
Fast Interrupt
The fast interrupt is a facility for faster interrupt processing by the CPU. This function has no effect on activation
requests for the DTC and DMAC.
By setting the FIEN bit in FIR to 1 and then setting the vector number of the interrupt source to be defined as the fast
interrupt in the FVCT[7:0] bits of FIR, interrupts from the source thus defined are output to the CPU for handling as the
fast interrupt.
The interrupt source selected for the fast interrupt has the highest priority regardless of the setting of the IPR[2:0] bits in
IPRi. When the CPU is engaged in processing for a non-maskable interrupt or a level-7 interrupt, it accepts the fast
interrupt after it has completed the current interrupt processing.
For details on the fast interrupt, see section 9, Exceptions.