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M(S)
M(S)
(PC
(PC
(PC
) : Contents of high-order 8 bits of program counter
H
(PC
)
: Contents of low-order 8 bits of program counter
L
: Contents of processor status register
(PS)
(S)
: Contents of stack pointer
M
: Memory
RTI
: Instruction for returning from interrupt routine to main routine
RTS
: Instruction for returning from subroutine to main routine
Fig. 2.1.3 Sequence of push onto/pop from a stack during interrupts and subroutine calls
On-going routine
Interrupt request
(PC
)
H
(S)
(S)–1
(PC
)
L
(S)
(S)–1
Subroutine
•
•
•
Execute RTS
(S)
(S)+1
)
M(S)
L
(S)
(S)+1
)
M(S)
H
7220 Group User's Manual
FUNCTIONAL DESCRIPTION
• • • • • • • •
M(S)
M(S)
Execute JSR
M(S)
• • • • • • • •
(PC
(PC
2.1 Central processing unit
(PC
)
H
(S)
(S)–1
(PC
)
L
(S)
(S)–1
(PS)
(S)
(S)–1
Interrupt routine
•
•
•
Execute RTI
(S)
(S)+1
(PS)
M(S)
(S)
(S)+1
)
M(S)
L
(S)
(S)+1
)
M(S)
H
2-5
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