NEC PD78214 - Manual (Page 107)

78
µ
PD78214 Sub-Series
(3) Address/data bus (AD0 through AD7)
Port 4 is used as the address/data automatically for external access.
Do not execute I/O instructions for port 4.
5.5.4 Built-In Pull-Up Resistor
Port 4 has built-in pull-up resistors. When port 4 must be pulled up, the built-in pull-up resistors should be used.
Use of the built-in pull-up resistors can reduce the number of the required components and the required
installation space.
Use of built-in pull-up resistors can be specified for all 8 bits of port 4 at one time (not independently of each other)
by the PUO4 bit of the pull-up-resistor-option register (PUO).
Use of built-in pull-up resistors can be specified for this port, regardless of the current mode (input or output) of
the port.
Fig. 5-24 Pull-Up-Resistor-Option Register Format
Caution For the µPD78213, port 4 is used as an address/data bus. Therefore, the PUO4 bit must be kept to be 0, and a built-in pull-up resistor
must not be connected. For the µPD78214, the same conditions must be maintained if port 4 is used as an address/data bus.
Remark Resetting the PUO to 00H can reduce the required current in the STOP mode.
0
7
PUO6
6
PUO5
5
PUO4
4
PUO3
3
PUO2
2
0
1
0
0
PUO
PUO4
Connected with port 4
Not connected with port 4
Specifies pull-up resistor connection of port 4
(00H when RESET is input)
0
1