M38044FFHKP datasheet(137/387 Pages) RENESAS

137 / 387 page

2-13

APPLICATION

2.2 Interrupt

Rev.1.00 Jan 14, 2005

REJ09B0212-0100Z

3804 Group (Spec.H)

2.2.4 Interrupt operation

When an interrupt request is accepted, the contents of the following registers just before acceptance of the

interrupt requests are automatically pushed onto the stack area in the order of ➀, ➁ and ➂.

➀High-order contents of program counter (PCH)

➁Low-order contents of program counter (PCL)

➂Contents of processor status register (PS)

After the contents of the above registers are pushed onto the stack area, the accepted interrupt vector

address enters the program counter and consequently the interrupt processing routine is executed.

When the RTI instruction is executed at the end of the interrupt processing routine, the contents of the

above registers pushed onto the stack area are restored to the respective registers in the order of ➂, ➁

and ➀; and the microcomputer resumes the processing executed just before acceptance of the interrupts.

Figure 2.2.8 shows an interrupt operation diagram.

Fig. 2.2.8 Interrupt operation diagram

Interrupt occurs

(Accepting interrupt request)

·······

Executing routine

Suspended

operation

Resume processing

: Operation commanded by software

: Internal operation performed automatically

Contents of program counter (high-order) are pushed onto stack

Contents of program counter (low-order) are pushed onto stack

Contents of processor status register are pushed onto stack

Contents of processor status register are popped from stack

Contents of program counter (low-order) are popped from stack

Contents of program counter (high-order) are popped from stack

RTI instruction

Interrupt

processing

routine

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