MITSUBISHI MICROCOMPUTERS
3822 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
I/O PORTS
b7
b0
Direction Registers (ports P2, P41-P47, and
P5-P7)
PULL register A
(PULLA: address 001616)
The 3822 group has 49 programmable I/O pins arranged in seven
I/O ports (ports P0–P2, P41–P47 and P5-P7). The I/O ports P2,
P41–P47 and P5-P7 have direction registers which determine the
input/output direction of each individual pin. Each bit in a direction
register corresponds to one pin, and each pin can be set to be in-
put port or output port.
P00–P07 pull-down
P10–P17 pull-down
P20–P27 pull-up
P34–P37 pull-down
P70, P71 pull-up
Not used (return “0” when read)
When “0” is written to the bit corresponding to a pin, that pin be-
comes an input pin. When “1” is written to that bit, that pin be-
comes an output pin.
b7
b0
PULL register B
If data is read from a pin set to output, the value of the port output
latch is read, not the value of the pin itself. Pins set to input are
floating. If a pin set to input is written to, only the port output latch
is written to and the pin remains floating.
(PULLB : address 001716)
P41–P43 pull-up
P44–P47 pull-up
P50–P53 pull-up
P54–P57 pull-up
P60–P63 pull-up
P64–P67 pull-up
Not used (return “0” when read)
Direction Registers (ports P0 and P1)
Ports P0 and P1 have direction registers which determine the in-
put/output direction of each individual port.
0: Disable
1: Enable
Each port in a direction register corresponds to one port, each port
can be set to be input or output. When “0” is written to the bit 0 of
a direction register, that port becomes an input port. When “1” is
written to that port, that port becomes an output port. Bits 1 to 7 of
ports P0 and P1 direction registers are not used.
Note: The contents of PULL register A and PULL register B
do not affect ports programmed as the output port.
Fig. 14 Structure of PULL register A and PULL register B
Ports P3 and P40
These ports are only for input.
Pull-up/Pull-down Control
By setting the PULL register A (address 001616) or the PULL reg-
ister B (address 001716), ports except for port P40 can control
either pull-down or pull-up (pins that are shared with the segment
output pins for LCD are pull-down; all other pins are pull-up) with
a program.
However, the contents of PULL register A and PULL register B do
not affect ports programmed as the output ports.
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MITSUBISHI [ Mitsubishi Group ]
