38K2 Datasheet, PDF (18/151 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

38K2 Group
Key Input Interrupt (Key-on Wake Up)
A Key-on wake up interrupt request is generated by applying a
falling edge to any pin of port P0 that have been set to input mode.
In other words, it is generated when AND of input level goes from
“1” to “0”. An example of using a key input interrupt is shown in
Figure 15, where an interrupt request is generated by pressing
one of the keys consisted as an active-low key matrix which inputs
to ports P00–P03.
Port PXx
“L” level output
P07 output
P06 output
P05 output
P04 output
P03 input
P02 input
P01 input
P00 input
PULL 0 register
Port P07
✽
Bit 7 = “0”
direction register = “1”
✽ ✽ _{Port P07}
latch
PULL 0 register
Port P06
✽
Bit 6 = “0”
direction register = “1”
✽ ✽ _{Port P06}
latch
PULL 0 register
Port P05
✽
Bit 5 = “0”
✽✽
direction register = “1”
Port P05
latch
PULL 0 register
Port P04
✽
Bit 4 = “0”
direction register = “1”
✽ ✽ _{Port P04}
latch
PULL 0 register
Bit 3 = “1”
Port P03
✽
✽✽
direction register = “0”
Port P03
latch
PULL 0 register
Bit 2 = “1”
Port P02
✽
✽✽
direction register = “0”
Port P02
latch
PULL 0 register
Bit 1 = “1”
Port P01
✽
✽ ✽ _{Port P01} ^{direction register = “0”}
latch
PULL 0 register
Bit 0 = “1”
Port P00
✽
direction register = “0”
✽ ✽ _{Port P00}
latch
Key input interrupt request
Port P0
Input reading circuit
✽ P-channel transistor for pull-up
✽ ✽ CMOS output buffer
Fig. 15 Connection example when using key input interrupt and port P0 block diagram
Rev.3.00 Oct 15, 2006 page 18 of 147
REJ03B0193-0300