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7641 Datasheet PDF : 149 Pages
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MITSUBISHI MICROCOMPUTERS
7641 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
I/O PORTS
Direction Registers
The I/O ports P0–P8 have direction registers which determine the
input/output direction of each individual pin. Each bit in a direction
register corresponds to one pin, 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 set to output, the value of the port output
latch is read, not the value of the pin itself. Pins set to input are float-
ing. If a pin set to input is written to, only the port output latch is
written to and the pin remains floating.
Slew Rate Control
By setting bits 0 to 5 of the port control register (address 001016) to
“1”, slew rate control is enabled. VIHL or CMOS level can be used as
a port P2 input level; CMOS or TTL level can be used as an input
level of master CPU bus interface.
Pull-up Control
By setting the port P2 pull-up control register (address 001216), pull-
up of each pin of port P2 can be controlled with a program.
However, the contents of port P2 pull-up control register do not affect
ports programmed as the output ports but as the input ports.
b7
b0
Port control register (address 001016)
PTC
Port P0 to P3 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P4 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P5 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P6 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P7 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P8 slew rate control bit (Note 1)
0: Disabled
1: Enabled
Port P2 input level select bit
0: Reduced VIHL level input (Note 2)
1: CMOS level input
Master CPU bus input level select bit
0: CMOS level input
1: TTLlevel input
b7
b0
Port P2 pull-up control register
(address 001216) PUP2
Port P20 pull-up control bit
0: Disabled
1: Enabled
Port P21 pull-up control bit
0: Disabled
1: Enabled
Port P22 pull-up control bit
0: Disabled
1: Enabled
Port P23 pull-up control bit
0: Disabled
1: Enabled
Port P24 pull-up control bit
0: Disabled
1: Enabled
Port P25 pull-up control bit
0: Disabled
1: Enabled
Port P26 pull-up control bit
0: Disabled
1: Enabled
Port P27 pull-up control bit
0: Disabled
1: Enabled
Notes 1: The slew rate function can reduce di/dt by modifying an internal
buffer structure.
2: The characteristics of VIHL level is basically the same as that of
TTL level. But, its switching center point is a little higher than
TTL’s. Refer to section “Recommended operating conditions”.
Fig. 11 Structure of port control and port P2 pull-up control
registers
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