NEC mPD780852 Series, Preliminary User'S Manual

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CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U14581EJ3V0UM00
(2) Pull-up resistor option register (PU0)
This register is used to set whether to use an on-chip pull-up resistor at port 0 or not. By setting the PU0, the
on-chip pull-up resistor of the corresponding port pin can be used.
PU0 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears this register to 00H.
Caution When the on-chip pull-up resistor is used, the pull-up resistor is not cut off even when the
port is set to the output mode. To use the port in the output mode, clear the corresponding
pull-up resistor option register to 0.
Figure 4-13. Pull-Up Resistor Option Register (PU0) Format
Address: FF30H After Reset: 00H R/W
Symbol 7 6 5 4 3 2 1 0
PU0 PU07 PU06 PU05 PU04 PU03 PU02 PU01 PU00
PU0n P0n Pin On-Chip Pull-Up Resistor Selection (n = 0 to 7)
0 On-chip pull-up resistor not used
1 On-chip pull-up resistor used