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Section 10 Interrupt Controller (INTC)
Rev. 4.00 Sep. 14, 2005 Page 238 of 982
REJ09B0023-0400
10.5 INTC Operation
10.5.1 Interrupt Sequence
The sequence of interrupt operations is described below. Figure 10.2 is a flowchart of the
operations.
1. The interrupt request sources send interrupt request signals to the interrupt controller.
2. The interrupt controller selects the highest-priority interrupt from the interrupt requests sent,
following the priority levels set in interrupt priority registers B to J (IPRB to IPRJ). Lower
priority interrupts are held pending. If two of these interrupts have the same priority level or if
multiple interrupts occur within a single module, the interrupt with the highest priority is
selected, according to table 10.5.
3. The priority level of the interrupt selected by the interrupt controller is compared with the
interrupt mask bits (I3 to I0) in the status register (SR) of the CPU. If the request priority level
is higher than the level in bits I3 to I0, the interrupt controller accepts the interrupt and sends
an interrupt request signal to the CPU.
4. Detection timing: The INTC operates, and notifies the CPU of interrupt requests, in
synchronization with the peripheral clock (Pφ). The CPU receives an interrupt at a break in
instructions.
5. The interrupt source code is set in the interrupt event register (INTEVT2).
6. The status register (SR) and program counter (PC) are saved to SSR and SPC, respectively.
7. The block bit (BL) and register bank bit (RB) in SR are set to 1.
8. The CPU jumps to the start address of the interrupt handler (the sum of the value set in the
vector base register (VBR) and H'00000600). This jump is not a delayed branch. The interrupt
handler may branch with the INTEVT2 register value as its offset in order to identify the
interrupt source. This enables it to branch to the handling routine for the individual interrupt
source.
Notes: 1. The interrupt mask bits (I3 to I0) in the status register (SR) are not changed by
acceptance of an interrupt in this LSI.
2. The interrupt source flag should be cleared in the interrupt handler. To ensure that an
interrupt request that should have been cleared is not inadvertently accepted again, read
the interrupt source flag after it has been cleared, and then execute an RTE instruction.