Renesas 7700 FAMILY User Manual page 58

When an interrupt request is accepted, the contents of the registers listed below immediately preceding the
acceptance of the interrupt request are automatically saved to the stack area in order of registers
Program bank register (PG)
Program counter (PC
Processor status register (PS
Figure 4.1.2 shows the state of the stack area just before entering the interrupt routine.
Execute the RTI instruction at the end of this interrupt routine to return to the routine that the microcomputer
was executing before the interrupt request was accepted. As the RTI instruction is executed, the register
contents saved in the stack area are restored in order of registers
routine executed before the acceptance of interrupt request and processing is resumed from it.
When an interrupt request is accepted and the RTI instruction is executed, the only above registers
are automatically saved and restored. When there are any other registers of which contents are necessary
to be kept, use software to save and restore them.
Fig. 4.1.2 State of stack area just before entering interrupt routine
, PC )
L H
, PS )
L H
Address
[S] – 5
Processor status register's low-order byte (PS
[S] – 4
Processor status register's high-order byte (PS
[S] – 3
Program counter's low-order byte (PC
[S] – 2
[S] – 1
Program counter's high-order byte (PC
Program bank register (PG)
[S]
[S] is an initial value that the stack pointer (S) indicates at
accepting an interrupt request. The S's contents become
[S] – 5 after saving the above registers.
7751 Group User's Manual
→ → , and a return is made to the
Stack area
INTERRUPTS
4.1 Overview
)
L
)
H
)
L
)
H
→ → .
to
4–3