M37544 Datasheet, PDF (21/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7544 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 21, where an interrupt request is generated by pressing
one of the keys provided as an active-low key matrix which uses
ports P00 to P03 as input ports.
Port PXx
“L” level output
P07 output
PULL register
bit 3 = “0”
Port P07
Direction register = “1”
*
**
Port P07
latch
Falling edge
detection
Key input interrupt request
P06 output
PULL register
bit 3 = “0”
Port P06
Direction register = “1”
*
**
Port P06
latch
Falling edge
detection
P05 output
PULL register
bit 3 = “0”
Port P05
Direction register = “1”
*
**
Port P05
latch
Falling edge
detection
P04 output
PULL register
bit 3 = “0”
Port P04
Direction register = “1”
*
**
Port P04
latch
Falling edge
detection
P03 input
PULL register
bit 2 = “1”
Port P03
Direction register = “0”
*
**
Port P03
latch
Falling edge
detection
Port P0
Input read circuit
P02 input
PULL register
bit 2 = “1”
Port P02
Direction register = “0”
*
**
Port P02
latch
Falling edge
detection
P01 input
PULL register
bit 1 = “1”
Port P01
Direction register = “0”
*
**
Port P01
latch
Falling edge
detection
P00 input
PULL register
bit 0 = “1”
Port P00
Direction register = “0”
*
**
Port P00
latch
Falling edge
detection
Port P00 key-on wakeup
selection bit
* P-channel transistor for pull-up
** CMOS output buffer
Fig. 21 Connection example when using key input interrupt and port P0 block diagram
Rev.1.04 2004.06.08 page 21 of 66
REJ03B0012-0104Z