H8SLASH3028F datasheet(128/923 Pages) RENESAS

128 / 923 page

Rev. 2.00, 09/03, page 98 of 890

5.4

Interrupt Operation

5.4.1

Interrupt Handling Process

The H8/3028 Group handles interrupts differently depending on the setting of the UE bit. When

UE = 1, interrupts are controlled by the I bit. When UE = 0, interrupts are controlled by the I and

UI bits. Table 5.4 indicates how interrupts are handled for all setting combinations of the UE, I,

and UI bits.

NMI interrupts are always accepted except in the reset and hardware standby states*. IRQ

interrupts and interrupts from the on-chip supporting modules have their own enable bits. Interrupt

requests are ignored when the enable bits are cleared to 0.

Note: * NMI input is sometimes disabled. For details see section 18.9, NMI Input Disabling

Conditions.

Table 5.4

UE, I, and UI Bit Settings and Interrupt Handling

SYSCR

CCR

Description

—

All interrupts are accepted. Interrupts with priority level 1 have higher

priority.

—

No interrupts are accepted except NMI.

—

All interrupts are accepted. Interrupts with priority level 1 have higher

priority.

NMI and interrupts with priority level 1 are accepted.

No interrupts are accepted except NMI.

UE = 1: Interrupts IRQ0 to IRQ5 and interrupts from the on-chip supporting modules can all be

masked by the I bit in the CPU’s CCR. Interrupts are masked when the I bit is set to 1, and

unmasked when the I bit is cleared to 0. Interrupts with priority level 1 have higher priority. Figure

5.4 is a flowchart showing how interrupts are accepted when UE = 1.

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