m30262f8gp Renesas Electronics Corporation., m30262f8gp Datasheet - Page 61

• Manufacturer Part Number: m30262f8gp
• Description: Renesas 16-bit Cmos Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

Interrupts
Saving Registers
Figure 1.9.6. State of stack before and after acceptance of interrupt request
In the interrupt sequence, only the contents of the flag register (FLG) and that of the program counter
(PC) are saved in the stack area.
First, the processor saves the four higher-order bits of the program counter, and 4 upper-order bits and 8
lower-order bits of the FLG register, 16 bits in total, in the stack area, then saves 16 lower-order bits of the
program counter. Figure 1.9.6 shows the state of the stack as it was before the acceptance of the
interrupt request, and the state the stack after the acceptance of the interrupt request.
To save other necessary registers, use the PUSHM instruction to save these registers except the stack
pointer (SP)at the beginning of the interrupt routine.
Address
m - 3
m - 2
m - 1
m - 4
m + 1
Stack status before interrupt request
is acknowledged
m
MSB
Preliminary Specifications Rev. 0.9
Specifications in this manual are tentative and subject to change.
Content of previous stack
Content of previous stack
Stack area
LSB
Renesas Technology Corp.
[SP]
Stack pointer
value before
interrupt occurs
Address
m - 4
m - 3
m - 2
m - 1
m
m + 1
Stack status after interrupt request
is acknowledged
MSB
Flag register
Content of previous stack
Content of previous stack
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Program counter (PC
Program counter (PC
(FLG
Flag register (FLG
Stack area
H
)
counter (PC
Program
L
)
L
M
)
)
H
LSB
)
M16C/26 Group
[SP]
New stack
pointer value
55