HD64F3028F25 Datasheet, PDF (130/925 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

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
UE
I
1
0
CCR
UI
—
1
—
0
0
—
1
0
1
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.
Rev. 2.00, 09/03, page 98 of 890