M16C62N Datasheet, PDF (49/213 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Interrupt
Mitsubishi microcomputers
M16C / 62N Group (80-pin)
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
The operation of saving registers carried out in the interrupt sequence is dependent on whether the
content of the stack pointer, at the time of acceptance of an interrupt request, is even or odd. If the
content of the stack pointer (Note) is even, the content of the flag register (FLG) and the content of the
program counter (PC) are saved, 16 bits at a time. If odd, their contents are saved in two steps, 8 bits at
a time. Figure 1.10.7 shows the operation of the saving registers.
Note: When any INT instruction in software numbers 32 to 63 has been executed, this is the stack pointer
indicated by the U flag. Otherwise, it is the interrupt stack pointer (ISP).
(1) Stack pointer (SP) contains even number
Address
Stack area
Sequence in which order
registers are saved
[SP] – 5 (Odd)
[SP] – 4 (Even)
Program counter (PCL)
[SP] – 3(Odd)
Program counter (PCM)
[SP] – 2 (Even)
Flag register (FLGL)
[SP] – 1(Odd)
Flag register Program
(FLGH) counter (PCH)
[SP] (Even)
(2) Saved simultaneously,
all 16 bits
(1) Saved simultaneously,
all 16 bits
Finished saving registers
in two operations.
(2) Stack pointer (SP) contains odd number
Address
Stack area
Sequence in which order
registers are saved
[SP] – 5 (Even)
[SP] – 4(Odd)
Program counter (PCL)
[SP] – 3 (Even)
Program counter (PCM)
[SP] – 2(Odd)
Flag register (FLGL)
[SP] – 1 (Even)
[SP] (Odd)
Flag register Program
(FLGH) counter (PCH)
(3)
(4) _{Saved simultaneously,}
all 8 bits
(1)
(2)
Finished saving registers
in four operations.
Note: [SP] denotes the initial value of the stack pointer (SP) when interrupt request is acknowledged.
After registers are saved, the SP content is [SP] minus 4.
Figure 1.10.7. Operation of saving registers
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