M37540M4 Datasheet, PDF (11/64 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

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MITSUBISHI MICROCOMPUTERS
7540 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
I/O Ports
[Direction registers] PiD
The I/O ports have direction registers which determine the input/out-
put direction of each pin. Each bit in a direction register corresponds
to one pin, and each pin can be set to be input or output.
When “1” is set to the bit corresponding to a pin, this pin becomes an
output port. When “0” is set to the bit, the pin becomes an input port.
When data is read from a pin set to output, not the value of the pin
itself but the value of port latch is read. Pins set to input are floating,
and permit reading pin values.
If a pin set to input is written to, only the port latch is written to and the
pin remains floating.
[Pull-up control register] PULL
By setting the pull-up control register (address 001616), ports P0 and
P3 can exert pull-up control by program. However, pins set to output
are disconnected from this control and cannot exert pull-up control.
[Port P1P3 control register] P1P3C
By setting the port P1P3 control register (address 001716), a CMOS
input level or a TTL input level can be selected for ports P10, P12,
P13, P36, and P37 by program.
b7
b0
Pull-up control register
(PULL: address 0016 16, initial value: 00 16)
P00 pull-up control bit
P01 pull-up control bit
P02, P03 pull-up control bit
P04 – P07 pull-up control bit
P30 – P33 pull-up control bit
P34 pull-up control bit
0 : Pull-up Off
P35, P36 pull-up control bit ^{1 : Pull-up On}
P37 pull-up control bit
Note 1: Pins set to output ports are disconnected from pull-up control.
2: Set the P35, P36 pull-up control bit to “1” (initial value: “0”) for 32-pin version.
Fig. 12 Structure of pull-up control register
b7
b0
Port P1P3 control register
(P1P3C: address 0017 16, initial value: 00 16)
P37/INT0 input level selection bit
0 : CMOS level
1 : TTL level
P36/INT1 input level selection bit
0 : CMOS level
1 : TTL level
P10,P12,P13 input level selection bit
0 : CMOS level
1 : TTL level
Not used
Note: Keep setting the P3 6/INT1 input level selection bit
to “0” (initial value) for 32-pin version.
Fig. 13 Structure of port P1P3 control register
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