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7542 Group
Key Input Interrupt (Key-On Wake-Up)
A key-on wake-up interrupt request is generated by applying "L"
level to any pin of port P0 that has been set to input mode.
In other words, it is generated when the AND of input level goes
from "1" to "0". An example of using a key input interrupt is shown
in Figure 25, where an interrupt request is generated by pressing
one of the keys provided as an active-low key matrix which uses
ports P0
to P0
as input ports.
0
3
P0
output
7
P0
output
6
P0
output
5
P0
output
4
P0
input
3
P0
input
2
P0
input
1
P0
input
0
Fig. 25 Connection example when using key input interrupt and port P0 block diagram
Rev.3.02
Oct 31, 2006
REJ03B0006-0302
Port PXx
"L" level output
PULL register
bit 3 = "0"
*
**
Port P0
7
latch
PULL register
bit 3 = "0"
*
**
Port P0
6
latch
Port P0
key-on wakeup
6
selection bit
PULL register
bit 3 = "0"
*
**
Port P0
5
latch
PULL register
bit 3 = "0"
*
**
Port P0
4
latch
Port P0
key-on wakeup
4
selection bit
PULL register
bit 2 = "1"
*
**
Port P0
3
latch
PULL register
bit 2 = "1"
*
**
Port P0
2
latch
PULL register
bit 1 = "1"
*
**
Port P0
1
latch
PULL register
bit 0 = "1"
*
**
Port P0
0
latch
Port P0
key-on wakeup
0
selection bit
Page 29 of 134
Port P0
7
Direction register = "1"
Falling edge
detection
Port P0
6
Direction register = "1"
Falling edge
detection
Port P0
5
Direction register = "1"
Falling edge
detection
Port P0
4
Direction register = "1"
Falling edge
detection
Port P0
3
Direction register = "0"
Falling edge
detection
Port P0
2
Direction register = "0"
Falling edge
detection
Port P0
1
Direction register = "0"
Falling edge
detection
Port P0
0
Direction register = "0"
Falling edge
detection
* P-channel transistor for pull-up
** CMOS output buffer
Key input interrupt request
Port P0
Input read circuit
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