UPD784938 Datasheet, PDF (153/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 6 PORT FUNCTIONS
6.5.4 On-chip pull-up resistors
Port 3 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 PUOL3 bit of the pull-
up resistor option register L (PUOL) and the port 3 mode register (PM3). When PUOL3 is 1, the on-chip pull-up resistors of the
pins for which input is specified by PM3 (PM3n = 1, n = 0 to 7) are enabled.
Also, the specification for use of the pull-up resistor is also valid for pins specified as control mode pins (pull-up resistors are
also connected to pins that function as output pins in the control mode). Therefore, if you do not want to connect the pull-up
resistors in the control mode, the contents of the corresponding bits of PM3 should be set to 0 (output mode).
Figure 6-35. 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
PUOL3 Port 3 Pull-Up Resistor Specification
0 Not used in port 3
1 Used in port 3
Remark When STOP mode is entered, setting PUOL to 00H is effective for reducing the current consumption.
Preliminary User’s Manual U13987EJ1V0UM00
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