M306V2 Mitsubishi, M306V2 Datasheet - Page 61

• Manufacturer Part Number: M306V2
• Description: SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER and ON-SCREEN DISPLAY CONTROLLER
• Manufacturer: Mitsubishi

Rev. 1.0
2.7.14 Returning from an Interrupt Routine
2.7.15 Interrupt Priority
2.7.16 Interrupt Priority Level Resolution Circuit
When two or more interrupts are generated simultaneously, this circuit selects the interrupt with the highest
priority level.
Figure 2.7.9 shows the circuit that judges the interrupt priority level.
Executing the REIT instruction at the end of an interrupt routine returns the contents of the flag register
(FLG) as it was immediately before the start of interrupt sequence and the contents of the program
counter (PC), both of which have been saved in the stack area. Then control returns to the program that
was being executed before the acceptance of the interrupt request, so that the suspended process re-
sumes.
Return the other registers saved by software within the interrupt routine using the POPM or similar in-
struction before executing the REIT instruction.
If there are two or more interrupt requests occurring at a point in time within a single sampling (checking
whether interrupt requests are made), the interrupt assigned a higher priority is accepted.
Assign an arbitrary priority to maskable interrupts (peripheral I/O interrupts) using the interrupt priority
level select bit. If the same interrupt priority level is assigned, however, the interrupt assigned a higher
hardware priority is accepted.
Priorities of the special interrupts, such as Reset (dealt with as an interrupt assigned the highest priority),
watchdog timer interrupt, etc. are regulated by hardware.
Figure 2.7.8 shows the priorities of hardware interrupts.
Software interrupts are not affected by the interrupt priority. If an instruction is executed, control branches
invariably to the interrupt routine.
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
MITSUBISHI MICROCOMPUTERS
M306V2ME-XXXFP
M306V2EEFP
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