SH7727 Datasheet, PDF (269/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

7.4 INTC Operation
Section 7 Interrupt Controller (INTC)
7.4.1 Interrupt Sequence
The sequence of interrupt operations is explained below. Figure 7.3 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 A to G (IPRA to IPRG). 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 default priority
or the highest priority within its IPR setting unit (as indicated in tables 7.4 and 7.5) is selected.
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 registers (INTEVT and INTEVT2).
6. The status register (SR) and program counter (PC) are saved to SSR and SPC, respectively.
7. The block bit (BL), mode bit (MD), 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 INTEVT and INTEVT2 register value as its offset in order to
identify the interrupt source. This enables it to branch to the processing 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 the SH7727.
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, then wait for the interval shown in
table 7.8 (Time for priority decision and SR mask bit comparison) before clearing the
BL bit or executing an RTE instruction.
Rev. 5.00 Dec 12, 2005 page 197 of 1034
REJ09B0254-0500