m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 96

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

Fig. 6.7.3 Push operation for registers
6.7.2 Push operation for registers
The push operation for registers performed in the INTACK sequence depends on whether the contents of
the stack pointer (S) at acceptance of an interrupt request are even or odd.
When the contents of the stack pointer (S) are even, the contents of the program counter (PC) and the
processor status register (PS) are simultaneously pushed in a unit of 16 bits. When the contents of the
stack pointer (S) are odd, each of PC and PS is pushed in a unit of 8 bits. Figure 6.7.3 shows the push
operation for registers.
In the INTACK sequence, only the contents of the program bank register (PG), program counter (PC), and
processor status register (PS) are pushed onto the stack area. Other necessary registers must be pushed
by software at the start of the interrupt routine.
By using the PSH instruction, all CPU registers, except the stack pointer (S), can be pushed with 1
instruction.
6.7 Sequence from acceptance of interrupt request until execution of interrupt routine
(1) When contents of stack pointer (S) are even
(2) When contents of stack pointer (S) are odd
[S] – 5 (even)
[S] – 3 (even)
[S] – 1 (even)
[S] – 4 (even)
[S] – 2 (even)
[S] – 4 (odd)
[S] – 2 (odd)
[S] – 5 (odd)
[S] – 3 (odd)
[S] – 1 (odd)
Address
Address
[S] (even)
[S] (odd)
[S] is the initial address that the stack pointer (S) indicates at acceptance of an interrupt request.
The S’s contents become “[S] – 5” after all of the above registers are pushed.
High-order byte of processor status register (PS
Low-order byte of processor status register (PS
High-order byte of processor status register (PS
Low-order byte of processor status register (PS
High-order byte of program counter (PC
High-order byte of program counter (PC
Low-order byte of program counter (PC
Low-order byte of program counter (PC
Program bank register (PG)
Program bank register (PG)
7905 Group User’s Manual Rev.1.0
H
H
L
L
)
)
)
)
L
H
L
H
)
)
)
)
Pushed in 3 times.
Pushed in 5 times.
Order for push
Order for push
Pushed in a unit of 16 bits.
Pushed in a unit of 16 bits.
Pushed in a unit of 8 bits.
INTERRUPTS
6-15