SH7018 Datasheet, PDF (78/431 Pages) Renesas Technology Corp – SuperH™ RISC engine

6.2 Interrupt Sources
There are three types of interrupt sources: NMI, IRQ, and on-chip peripheral modules. Each
interrupt has a priority expressed as a priority level (0 to 16, with 0 the lowest and 16 the highest).
Giving an interrupt a priority level of 0 masks it.
6.2.1 NMI Interrupts
The NMI interrupt has priority 16 and is always accepted. Input at the NMI pin is detected by
edge. Use the NMI edge select bit (NMIE) in the interrupt control register (ICR) to select either
the rising or falling edge. NMI interrupt exception processing sets the interrupt mask level bits (I3
to I0) in the status register (SR) to level 15.
6.2.2 IRQ Interrupts
IRQ interrupts are requested by input from pins IRQ0 to IRQ3, IRQ6, and IRQ7. Set the IRQ
sense select bits (IRQ0S to IRQ3S, IRQ6S, and IRQ7S) of the interrupt control register (ICR) to
select low level detection or falling edge detection for each pin. The priority level can be set from
0 to 15 for each pin using the interrupt priority registers A and B (IPRA, IPRB).
When IRQ interrupts are set to low level detection, an interrupt request signal is sent to the INTC
during the period the IRQ pin is low level. Interrupt request signals are not sent to the INTC when
the IRQ pin becomes high level. Interrupt request levels can be confirmed by reading the IRQ
flags (IRQ0F to IRQ3F, IRQ6F, and IRQ7F) of the IRQ status register (ISR).
When IRQ interrupts are set to falling edge detection, interrupt request signals are sent to the
INTC upon detecting a change on the IRQ pin from high to low level. IRQ interrupt request
detection results are maintained until the interrupt request is accepted. Confirmation that IRQ
interrupt requests have been detected is possible by reading the IRQ flags (IRQ0F to IRQ3F,
IRQ6F, and IRQ7F) of the IRQ status register (ISR), and by writing a 0 after reading a 1, IRQ
interrupt request detection results can be withdrawn.
In IRQ interrupt exception processing, the interrupt mask bits (I3 to I0) of the status register (SR)
are set to the priority level value of the accepted IRQ interrupt.
62