M38258MCM Datasheet, PDF (14/70 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS
3825 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
I/O PORTS
Direction Registers
The 3825 group has 43 programmable I/O pins arranged in seven
I/O ports (ports P16, P17 P2, P4–P6, P71–P77, P80 and P81). The
I/O ports have direction registers which determine the input/output
direction of each individual pin. (Ports P16 and P17 are shared
with bits 6 and 7 of the port P1 output control register). Each bit in
a direction register 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 be-
comes an output pin.
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.
Port P1 Output Control Register
Bit 0 of the port P1 output control register (address 000316) en-
ables control of the output of ports P10 to P15.
When the bit is set to “1”, the port output function is valid.
In this case, setting of the PULL register A to ports P10 to P15 is
invalid.
When resetting, bit 0 of the port P1 output control register is set to
“0” (the port output function is invalid.)
Pull-up/Pull-down Control
By setting the PULL register A (address 001616) or the PULL reg-
ister B (address 001716), ports P0 to P8 except P70 can control ei-
ther 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. (except for ports
P0 and P3).
Ports P0 and P3 share the port output control function with bit 0 of
the PULL register A. When set to “1”, the port output function is in-
valid (Pull-down is valid).
When set to “0”, the port output function is valid (Pull-down is in-
valid).
The PULL register A setting is invalid for pins set to segment out-
put with the segment output enable register.
b7
b0
PULL register A
(PULLA : address 001616)
P0, P10–P15, P3 pull-down
(shared with P0 and P3 output
control : refer to the text)
P16–P17 pull-up
P20–P27 pull-up
P80, P81 pull-up
P40–P43 pull-up
P44–P47 pull-up
Not used (return “0” when read)
b7
b0
PULL register B
(PULLB : address 001716)
P50–P53 pull-up
P54–P57 pull-up
P60–P63 pull-up
P64–P67 pull-up
P71–P73 pull-up
P74–P77 pull-up
Not used (return “0” when read)
0 : Disable
1 : Enable
Note : The contents of PULL register A and PULL register B
do not affect ports programmed as the output port.
Fig. 11 Structure of PULL register A and PULL register B
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