m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 101

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

INTERRUPTS
Fig. 6.10.3 INT
Fig. 6.10.4 Occurrence of INT
6-20
6.10 External interrupts
6.10.2 Functions of INT
Figure 6.10.3 shows an INT
(1) Functions when edge sense is selected
(2) Functions when level sense is selected
Pin INT
Level at pin INT
In this case, the interrupt request bit has the same function as that of an internal interrupt. That is,
when an interrupt request occurs, the interrupt request bit is set to “1” and retains this state until the
interrupt request is accepted. When this bit is cleared to “0” by software, the interrupt request is
cancelled; when this bit is set to “1” by software, the interrupt request can occur.
In this case, the interrupt request bit is ignored.
INT
at pin INT
request is accepted, this interrupt request is not retained. (See Figure 6.10.4.)
Valid level
Invalid level
i
i
interrupt requests continuously occur while the level at pin INT
i
i
Interrupt request
i
changes from the valid level to the invalid level
1
: This means the level selected by the polarity select bit (bit 4 at addresses 7D
Invalid
2
Edge detection
6E
: This means the reversed level of “valid level”
Valid
Main routine
16
, 6F
circuit
i
interrupt request bit
i
16
interrupt request.
, FD
i
interrupt request when level sense is selected
16
First interrupt routine
to FF
7905 Group User’s Manual Rev.1.0
Interrupt request is accepted.
16
)
Interrupt request bit
Data bus
Second interrupt
routine
2
before the corresponding INT
Level sense/Edge sense
select bit
0
1
When the level at pin INT
to the invalid level before the INT
interrupt request is accepted, this
interrupt request is not retained.
Return to main routine.
i
Third interrupt
is the valid level
routine
Interrupt request
Main routine
1
; when the level
i
changes
i
16
i
interrupt
to 7F
16
,