3820_03 Datasheet, PDF (104/349 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
2.2 Interrupts
(2) Processing upon acceptance of an interrupt request
Upon acceptance of an interrupt request, the following operations are automatically performed.
ŒThe 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.
ŽConcurrently 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.
Program counter
PCL Program counter (high-order)
PCH Program counter (low-order)
Interrupt disable flag = “0”
Stack area
Stack pointer
S
(S)
(S)
Interrupt
request is
accepted
Program counter
PCL
Vector address
PCH (from Interrupt vector area)
Stack pointer
S
(S) – 3
Interrupt disable flag = “1”
Stack area
(s) – 3
Processor status register
Program counter (low-order)
(S) Program counter (high-order)
Fig. 2.2.2 Changes of stack pointer and program counter upon acceptance of interrupt request
3820 GROUP USER’S MANUAL
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