3822 datasheet(83/328 Pages) RENESAS

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2.2 Interrupts

APPLICATION

2–17

3822 GROUP USER’S MANUAL

(2) Processing upon acceptance of an interrupt request

Upon acceptance of an interrupt request, the following operations are automatically performed.

The processing being executed is stopped.

The contents of the program counter and the processor status register are pushed onto the stack

area. Figure 2.2.2 shows changes of the stack pointer and the program counter upon acceptance

of an interrupt request.

Concurrently with the push operation, the jump destination address (the beginning address of the

interrupt processing routine) of the occurring interrupt stored in the vector address is set in the

program counter, then the interrupt processing routine is executed.

After the interrupt processing routine is started, the corresponding interrupt request bit is automati-

cally cleared to “0.” The interrupt disable flag is set to “1” so that multiple interrupts are disabled.

Accordingly, for executing the interrupt processing routine, it is necessary to set the jump destination

address in the vector area corresponding to each interrupt.

Fig. 2.2.2 Changes of stack pointer and program counter upon acceptance of interrupt request

Interrupt disable flag = “0”

Program counter

Stack pointer

Program counter (high-order)

Program counter (low-order)

PCL

PCH

(S)

Program counter

Stack pointer

PCL

PCH

(S) – 3

Vector address

(from Interrupt vector area)

Interrupt disable flag = “1”

Interrupt

request is

accepted

Stack area

(S)

Processor status register

Program counter (low-order)

Program counter (high-order)

(S)

(s) – 3

Stack area

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