M37544 RENESAS [Renesas Technology Corp], M37544 Datasheet - Page 21

• Manufacturer Part Number: M37544
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
• Manufacturer: RENESAS [Renesas Technology Corp]

Rev.1.04
REJ03B0012-0104Z
7544 Group
Fig. 21 Connection example when using key input interrupt and port P0 block diagram
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 21, where an interrupt request is generated by pressing
one of the keys provided as an active-low key matrix which uses
ports P0
0
to P0
2004.06.08
3
as input ports.
page 21 of 66
P0
P0
P0
P0
P0
P0
P0
P0
7
6
5
4
2
output
output
output
output
3
1
0
input
input
input
input
Port PXx
“L” level output
Port P0
selection bit
*
*
*
*
*
*
*
*
0
PULL register
bit 3 = “0”
PULL register
bit 3 = “0”
PULL register
bit 3 = “0”
PULL register
bit 3 = “0”
PULL register
bit 2 = “1”
PULL register
bit 2 = “1”
PULL register
bit 1 = “1”
PULL register
bit 0 = “1”
key-on wakeup
**
**
**
**
**
**
**
**
Port P0
latch
Port P0
latch
Port P0
latch
Port P0
latch
Port P0
latch
Port P0
latch
Port P0
latch
Port P0
latch
7
6
5
4
3
2
1
0
Port P0
Direction register = “1”
Port P0
Direction register = “1”
Port P0
Direction register = “1”
Port P0
Direction register = “1”
Port P0
Direction register = “0”
Port P0
Direction register = “0”
Port P0
Direction register = “0”
Port P0
Direction register = “0”
7
6
5
4
3
2
1
0
Falling edge
detection
Falling edge
detection
Falling edge
detection
Falling edge
detection
Falling edge
detection
Falling edge
detection
Falling edge
detection
Falling edge
detection
** CMOS output buffer
* P-channel transistor for pull-up
Key input interrupt request
Port P0
Input read circuit