7470/7471/7477/7478 GROUP USER’S MANUAL
HARDWARE
1.10 I/O pins
1-47
Port
P0
P10 to P13
P15, P17
P2 (7470/7471 group)
P4
P14, P16
P2 (7477/7478 group)
P30 to P33
P5
(Note 7)
VREF
AVSS
Terminations
,
(Note 1)
,
(Note 3)
,
(Note 1)
×
,
×
Pull down (connect to
VSS) ports through a
resistor (Note 2)
,
(Note 5)
,
(Note 5)
,
(Note 6)
,
(Note 6)
,
(Note 8)
×
Connect
to
VCC
×
,
(Note 6)
,
(Note 6)
×
,
×
(4) Termination of unused pins
Table 1.10.2 shows a termination of unused pins.
Table 1.10.2 Termination of unused pins
Notes 1: A pin that can be opened at the unused time has a circuit that does not allow a current to flow
into itself unless any read signal is internally input even if a medium-level input is applied at the
open state.
2: For programmable I/O ports, do not connect two or more ports together through a resistor to VCC
or VSS.
3: Note the following when setting them to the output mode and making the pins open.
The ports function as input ports in the period from reset release till switching the ports to the
output mode by software. Accordingly, the power source current may be increased depending
on the input levels of the pins.
If the Port direction register has been changed into the input mode by runaway or noise, re-set
the Port direction register to the output mode periodically by software.
4: To pull up a pin, set the Port direction register and the Port latch so that this pin may be into the
input mode or “H” output state.
5: To pull down a pin, set the Port direction register, the Port pull-up control register and the Port
latch so that this pin may be put in the no pull-up transistor state in the input mode or in the “L”
output state.
6: These pins are connect to the VCC or VSS without a resistor when the wiring is the shortest.
However, they are connect to the VCC or VSS through a resistor. In addition, the P33 pin of the
built-in programmable ROM version is used in common with the VPP pin, insert a resistor of about
5 k in series and connect by the shortest wiring.
7: When using neither the P50 pin nor the P51 pin (used in common with the XCIN and XCOUT pin),
set bit 4 of the CPU mode register to “0” (P50 and P51 functions).
8: To pull down a pin, set the port pull-up control register so that a pull-up transistor will not be
provided for this pin.
Pull-up (connect to VCC)
ports through a resistor
(Note 2)
,
(Note 4)
,
(Note 4)
,
(Note 6)
,
(Note 6)
,
×
Connect
to
VSS
×
,
(Note 6)
,
(Note 6)
×
,
Open