M30222 Datasheet, PDF (35/237 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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Specifications in this manual are tentative and subject to change
MITSUBISHI MICROCOMPUTERS
M30222 Group
Rev. G
Overview of Interrupts
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Overview of Interrupts
Types of Interrupts
Figure 1.21 lists the types of interrupts.
Software
Undefined instruction (UND instruction)
Overflow (INTO instruction)
BRK instruction
INT instruction
Interrupt
Hardware
Address matched
Special
Reset
NMI
DBC
Watchdog timer
Single step
Peripheral I/O (Note)
Note: Peripheral I/O interrupts are generated by the peripheral functions built into the microcomputer system.
Figure 1.21. Classification of interrupts
• Maskable interrupt :
An interrupt which can be enabled (disabled) by the interrupt enable flag (I
flag) or whose interrupt priority can be changed by priority level.
• Non-maskable interrupt : An interrupt which cannot be enabled (disabled) by the interrupt enable
flag (I flag) or whose interrupt priority cannot be changed by priority level.
Software Interrupts
A software interrupt occurs when executing certain instructions. Software interrupts are non-maskable
interrupts.
• Undefined instruction interrupt
An undefined instruction interrupt occurs when executing the UND instruction.
• Overflow interrupt
An overflow interrupt occurs when an executing arithmetic instruction overflows. The following instruc-
tions will set an O flag when an overflow occurs :
ABS, ADC, ADCF, ADD, CMP, DIV, DIVU, DIVX, NEG, RMPA, SBB, SHA, SUB
• BRK interrupt
A BRK interrupt occurs when executing the BRK instruction.
• INT interrupt
An INT interrupt occurs when specifying one of the software interrupt numbers 0 through 63 and execut-
ing the INT instruction. Software interrupt numbers 0 through 31 are assigned to peripheral I/O inter-
rupts, so executing the INT instruction executes the same interrupt routine as the peripheral I/O interrupt.
The stack pointer (SP), used for the INT interrupt, is dependent on which software interrupt number is
selected.
As far as software interrupt numbers 0 through 31 are concerned, the microcomputer saves the stack
pointer assignment flag (U flag) when it accepts an interrupt request. The U flag is set to "0" selecting the
interrupt stack pointer then the interrupt sequence is executed. When returning from the interrupt routine,
the U flag is returned to its previous state before accepting the interrupt request.
As far as software numbers 32 through 63 are concerned, the stack pointer does not change.
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