Rev.3.00
2004.08.06
page 29 of 155
REJ03B0010-0300Z
4584 Group
PRELIMINARY
Notice: This is not a final specification.
Some parametric limits are subject to change.
(4) Notes on External 0 interrupt
Note [1] on bit 3 of register I1
When the input of the INT0 pin is controlled with the bit 3 of reg-
ister I1 in software, be careful about the following notes.
Depending on the input state of the P30/INT0 pin, the external 0
interrupt request flag (EXF0) may be set when the bit 3 of regis-
ter I1 is changed. In order to avoid the occurrence of an
unexpected interrupt, clear the bit 0 of register V1 to “0” (refer to
Figure 18 ) and then, change the bit 3 of register I1.
In addition, execute the SNZ0 instruction to clear the EXF0 flag
to “0” after executing at least one instruction (refer to Figure 18
).
Also, set the NOP instruction for the case when a skip is per-
formed with the SNZ0 instruction (refer to Figure 18 ).
LA
4
; (02)
TV1A
; The SNZ0 instruction is valid ...........
LA
8
; (12)
TI1A
; Control of INT0 pin input is changed
NOP
...........................................................
SNZ0
; The SNZ0 instruction is executed
(EXF0 flag cleared)
NOP
...........................................................
: these bits are not used here.
Fig. 18 External 0 interrupt program example-1
Note [2] on bit 3 of register I1
When the bit 3 of register I1 is cleared to “0” , the RAM back-up
mode is selected and the input of INT0 pin is disabled, be careful
about the following notes.
When the input of INT0 pin is disabled (register I13 = “0”), set the
key-on wakeup function to be invalid (register K20 = “0”) before
system enters to the RAM back-up mode. (refer to Figure 19).
LA
0
; (02)
TK2A
; Input of INT0 key-on wakeup invalid ..
DI
EPOF
POF
; RAM back-up
: these bits are not used here.
Fig. 19 External 0 interrupt program example-2
Note on bit 2 of register I1
When the interrupt valid waveform of the P30/INT0 pin is
changed with the bit 2 of register I1 in software, be careful about
the following notes.
Depending on the input state of the P30/INT0 pin, the external 0
interrupt request flag (EXF0) may be set when the bit 2 of regis-
ter I1 is changed. In order to avoid the occurrence of an
unexpected interrupt, clear the bit 0 of register V1 to “0” (refer to
Figure 20) and then, change the bit 2 of register I1.
In addition, execute the SNZ0 instruction to clear the EXF0 flag
to “0” after executing at least one instruction (refer to Figure
20).
Also, set the NOP instruction for the case when a skip is per-
formed with the SNZ0 instruction (refer to Figure 20).
LA
4
; (02)
TV1A
; The SNZ0 instruction is valid ...........
LA
12
; (12)
TI1A
; Interrupt valid waveform is changed
NOP
...........................................................
SNZ0
; The SNZ0 instruction is executed
(EXF0 flag cleared)
NOP
...........................................................
: these bits are not used here.
Fig. 20 External 0 interrupt program example-3