UPD784938 Datasheet, PDF (159/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 6 PORT FUNCTIONS
6.6.4 On-chip pull-up resistors
Port 4 incorporates pull-up resistors. Use of these internal resistors when pull-up is necessary enables the number of parts
and the mounting area to be reduced.
Whether or not an on-chip pull-up resistor is to be used can be specified for each pin by setting the PUOL4 bit of the pull-
up resistor option register L (PUOL) and the port 4 mode register (PM4).
When PUOL4 is 1, the on-chip pull-up resistors of the pins for which input is specified by the PM4 for port 4 (PM4n = 1,
n = 0 to 7) are enabled .
Figure 6-41. Pull-Up Resistor Option Register L (PUOL) Format
PUOL
7
6
5
4
3
2
1
0 Address After reset R/W
0 PUOL6 PUOL5 PUOL4 PUOL3 PUOL2 PUOL1 PUOL0 0FF4EH
00H R/W
PUOL4 Port 4 Pull-Up Resistor Specification
0 Not used in port 4
1 Used in port 4
Caution When using the port 4 of the µPD784938 as an address/data bus pin, be sure to clear PUOL4 to 0 to
disconnect the on-chip pull-up resistor.
Remark When STOP mode is entered, setting PUOL to 00H is effective for reducing the current consumption.
Preliminary User’s Manual U13987EJ1V0UM00
159