5
MITSUBISHI MICROCOMPUTERS
4551 Group
SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER for
INFRARED REMOTE CONTROL TRANSMITTER
MULTIFUNCTION
Pin
D
5
D
6
D
7
P2
0
P2
1
P2
2
P2
3
Notes 1: Pins except above have just single function.
2: The port D
5
is the output port and ports P2
0
–P2
3
are the input ports.
CONNECTIONS OF UNUSED PINS
Pin
D
0
–D
4
D
5
/INT
D
6
/X
CIN
D
7
/X
COUT
P 2
0
/
SEG
1 6
– P 2
3
/
SEG
19
Note: In order to connect ports P1
0
–P1
3
to V
SS
, turn off their pull-up transistors (Pull-up control register PU0
i
=“0”) by software. In
order to make these pins open, turn on their pull-up transistors (register PU0
i
=“1”) by software, or turn off their pull-up
transistors (register PU0i=“0”) and set the output latch to “0” (
i = 0, 1, 2, or 3
).
Be sure to select the key-on wakeup function and the pull-up function with every one port.
Connection
Connect to V
SS
, or set the output latch to
“0” and open.
Select ports D
6
and D
7
and connect to V
SS
,
or set the output latch to “0” and open.
Select port P2 and connect to V
SS
, or select
the segment output function and open.
Connection
Open
Open
Open
Set the output latch to “1” and open.
Open or connect to V
SS
(Note)
Pin
CARR
SEG
0
–SEG
15
COM
0
–COM
3
P0
0
–P0
3
P1
0
–P1
3
Multifunction
INT
X
CIN
X
COUT
SEG
16
SEG
17
SEG
18
SEG
19
Multifunction
D
5
D
6
D
7
P2
0
P2
1
P2
2
P2
3
Pin
INT
X
CIN
X
COUT
SEG
16
SEG
17
SEG
18
SEG
19
PORT FUNCTION
Port
Port D
Port P0
Port P1
Port P2
Control
bits
1
4
4
4
Control
instructions
SD
RD
CLD
OP0A
IAP0
OP1A
IAP1
IAP2
Control
registers
MR
PU0
Output structure
N-channel open-drain
N-channel open-drain
N-channel open-drain
Input/
Output
Output
(8)
I/O
(4)
I/O
(4)
Input
(4)
Remark
Pull-up functions
Key-on wakeup functions
Pull-up functions
(programmable)
Key-on wakeup functions
(programmable)
Pin
D
0
–D
4
, D
5
/INT,
D
6
/X
CIN
,
D
7
/X
COUT
P0
0
–P0
3
P1
0
–P1
3
P2
0
/SEG
16
–
P2
3
/SEG
19
(Note in order to set the output latch to “0” and make pins open)
After system is released from reset, a port is in a high-impedance state until the output latch of the port is set to “0” by software.
Accordingly, the voltage level of pins is undefined and the excess of the supply current may occur.
To set the output latch periodically is recommended because the value of output latch may change by noise or a program run away
(caused by noise).
(Note in order to connect unused pins to V
SS
or V
DD
)
To avoid noise, connect the unused pins to V
SS
or V
DD
at the shortest distance using a thick wire.