![](http://datasheet.mmic.net.cn/30000/M30956FKTGP_datasheet_2359453/M30956FKTGP_115.png)
10. Interrupts
10.4
High-Speed Interrupt
The high-speed interrupt executes an interrupt sequence in five cycles and returns from the interrupt routine in
three cycles in single-speed mode. When the FSIT bit in the RLVL register is set to 1 (interrupt priority level 7
is be used for the high-speed interrupt), an interrupt that bits ILVL2 to ILVL0 in the interrupt control register
are set to 111b (level 7) becomes the high-speed interrupt.
Only one interrupt can be set as the high-speed interrupt. To use the high-speed interrupt, do not set multiple
interrupts to interrupt priority level 7. Set the DMAII bit in the RLVL register to 0 (interrupt priority level 7 is
used for normal interrupt) to use the high-speed interrupt.
Set the start address of a high-speed interrupt routine in the VCT register.
When the high-speed interrupt is acknowledged, the FLG register is saved into the SVF register and PC is saved
into the SVP register. A program is executed from an address indicated by the VCT register.
Use the FREIT instruction to return from a high-speed interrupt routine. Values saved into registers SVF and
SVP are restored to the FLG register and PC by executing the FREIT instruction.
The high-speed interrupt and DMA2 and DMA3 use the same register. When using the high-speed interrupt,
neither DMA2 nor DMA3 is available. DMA0 and DMA1 can still be used.
Figure 10.2 shows a procedure to use high-speed interrupt.
Figure 10.2
Procedure to Use High-Speed Interrupt
Set I flag to 0
FSIT bit in the RLVL register to 1
DMAII bit in the RLVL register to 0
Set I flag to 1
Operate peripheral functions
Set the start address of a high-speed interrupt
routine in the VCT regsiter
Set bits ILVL2 to ILVL0 in the interrupt control
register to 111b (level 7)
Interrupt enable
Interrupt disable
Interrupt priority level 7 is used for the high-speed interrupt
Interrupt priority level 7 is used for interrupt
Set the interrupt priority level in the interrupt control register
for the peripheral function, which is to be the high-speed
interrupt source.
Set the peripheral function, which is to be the high-
speed interrupt source
Start
End