tmp89fm42 TOSHIBA Semiconductor CORPORATION, tmp89fm42 Datasheet - Page 71

• Manufacturer Part Number: tmp89fm42
• Description: 8 Bit Microcontroller
• Manufacturer: TOSHIBA Semiconductor CORPORATION

RA003
Example :Using PUSH and POP instructions
3.5.3 Saving/restoring general-purpose registers
SP
3.5.3.1
At Acceptance of
the interrupt service routine.
case, acceptable interrupt sources are selectively enabled by the individual interrupt enable flags.
before setting IMF to “1”. As for non-maskable interrupt, keep interrupt service shorter compared with length
between interrupt requests.
includes IMF) are automatically saved on the stack, but the general purpose registers are not. These registers
must be saved by software if necessary. When multiple interrupt services are nested, it is also necessary to
avoid using the same data memory area for saving registers. The following methods are used to save/restore the
general-purpose registers.
A maskable interrupt is not accepted until the IMF is set to “1” even if the maskable interrupt is requested in
In order to utilize nested interrupt service, the IMF must be set to “1” in the interrupt service program. In this
To avoid overloaded nesting, clear the individual interrupt enable flag whose interrupt is currently serviced,
During interrupt acceptance processing, the program counter (PC) and the program status word (PSW,
PINTxx
an Interrupt
PSW
PC
PC
Using PUSH and POP instructions
To save only a specific register, PUSH and POP instructions are available.
H
L
Figure 3-3 Saving/restoring general-purpose registers
PUSH
Interrupt processing
POP
RETI
SP
PUSH instruction
At execution of
PSW
PC
PC
W
A
H
L
WA
WA
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SP
; Save WA register
; Restore WA register
; RETURN
POP instruction
At execution of
PSW
PC
PC
H
L
SP
an RETI instruction
At execution of
Address
(Example)
b-4
b-3
b-2
b-1
b
TMP89FM42