
8
3851 Group
(Built-in 16 KB ROM)
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
MITSUBISHI MICROCOMPUTERS
Pin
Name
Input/Output
I/O Structure Non-Port Function
Ref.No.
Table 2 I/O port function
Related SFRs
I/O PORTS
The I/O ports have direction registers which determine the input/
output direction of each individual pin. Each bit in a direction reg-
ister corresponds to one pin, and each pin can be set to be input
port or output port.
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
becomes an output pin.
If data is read from a pin which is 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.
Port P0
Port P1
Port P3
Input/output,
individual
bits
CMOS compatible
input level
CMOS 3-state output
Sub-clock generating
circuit
CPU mode register
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
P00–P07
P10–P17
P20/XCOUT
P21/XCIN
P22/SDA1
P23/SCL1
P24/SDA2/RxD
P25/SCL2/TxD
Port P2
P26/SCLK
P27/CNTR0/SRDY
P30/AN0—
P34/AN4
P40/CNTR1
P41/INT0—
P43/INT2
P44/INT3/PWM
Port P4
CMOS compatible
input level
CMOS/SMBUS input
level (when selecting
I
2
C-BUS interface
function)
N-channel open-drain
output
CMOS compatible
input level
CMOS/SMBUS input
level (when selecting
I
2
C-BUS interface
function)
CMOS 3-state output
N-channel open-drain
output (when
selecting I
2
C-BUS
interface function)
CMOS compatible
input level
CMOS 3-state output
I
2
C-BUS interface func-
tion I/O
I
2
C-BUS interface func-
tion I/O
Serial I/O function I/O
Serial I/O function I/O
Serial I/O function I/O
Timer X function I/O
A-D conversion input
I
2
C control register
I
2
C control register
Serial I/O control
register
Serial I/O control
register
Serial I/O control
register
Timer XY mode register
A-D control register
Timer Y function I/O
External interrupt input
External interrupt input
PWM output
Timer XY mode register
Interrupt edge selection
register
Interrupt edge selection
register
PWM control register
(13)
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