HD64F2638F20J Datasheet, PDF (176/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 5 Interrupt Controller
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
5.4.3 Interrupt Control Mode 2
Eight-level masking is implemented for IRQ interrupts and on-chip supporting module interrupts
by comparing the interrupt mask level set by bits I2 to I0 of EXR in the CPU with IPR.
Figure 5-6 shows a flowchart of the interrupt acceptance operation in this case.
[1] If an interrupt source occurs when the corresponding interrupt enable bit is set to 1, an
interrupt request is sent to the interrupt controller.
[2] When interrupt requests are sent to the interrupt controller, the interrupt with the highest
priority according to the interrupt priority levels set in IPR is selected, and lower-priority
interrupt requests are held pending. If a number of interrupt requests with the same priority are
generated at the same time, the interrupt request with the highest priority according to the
priority system shown in table 5-4 is selected.
[3] Next, the priority of the selected interrupt request is compared with the interrupt mask level set
in EXR. An interrupt request with a priority no higher than the mask level set at that time is
held pending, and only an interrupt request with a priority higher than the interrupt mask level
is accepted.
[4] When an interrupt request is accepted, interrupt exception handling starts after execution of the
current instruction has been completed.
[5] The PC, CCR, and EXR are saved to the stack area by interrupt exception handling. The PC
saved on the stack shows the address of the first instruction to be executed after returning from
the interrupt handling routine.
[6] The T bit in EXR is cleared to 0. The interrupt mask level is rewritten with the priority level of
the accepted interrupt.
If the accepted interrupt is NMI, the interrupt mask level is set to H'7.
[7] A vector address is generated for the accepted interrupt, and execution of the interrupt
handling routine starts at the address indicated by the contents of that vector address.
Page 126 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010