NEC 78K0 Series User Manual page 128

(3) Pull-up resistor option registers (PU0, PU1, PU3 to PU5, PU7, PU12, and PU14)
These registers specify whether the on-chip pull-up resistors of P00 to P06, P10 to P17, P30 to P33, P40 to P43,
P50 to P53, P70 to P77, P120, or P140 and P141 are to be used or not. On-chip pull-up resistors can be used in
1-bit units only for the bits set to input mode of the pins to which the use of an on-chip pull-up resistor has been
specified in PU0, PU1, PU3 to PU5, PU7, PU12, and PU14. On-chip pull-up resistors cannot be connected to
bits set to output mode and bits used as alternate-function output pins, regardless of the settings of PU0, PU1,
PU3 to PU5, PU7, PU12, and PU14.
These registers can be set by a 1-bit or 8-bit memory manipulation instruction.
Reset signal generation sets these registers to 00H.
Symbol 7 6
PU0 0 PU06
PU1
PU17 PU16
PU3 0 0
PU4
128
CHAPTER 5 PORT FUNCTIONS
Figure 5-28. Format of Pull-up Resistor Option Register
5 4 3
PU05 PU04 PU03
PU15 PU14 PU13
0 0 PU33
PU43
Preliminary User's Manual U17260EJ3V1UD
2 1 0
PU02 PU01 PU00
PU12 PU11 PU10
PU32 PU31 PU30
PU42 PU41 PU40
Address After reset R/W
FF30H 00H R/W
FF31H 00H R/W
FF33H 00H R/W
FF34H 00H R/W