NEC 78K0S/K 1+ Series Application Note page 24

(3) Setting the connection of internal pull-up resistors to input ports
The PUxx registers are used to set whether internal pull-up resistors are to be connected to the input ports.
Internal pull-up resistors are not connected after reset release.
The PUxx format is described, taking the PU2 register as an example.
In this sample program, port 4 is set as described in
PU2
0 0 0
Caution Bits 7 to 4 must be set to 0.
[Example 1] • Setting P20 to P23 as output ports
• Setting the P20 to P22 output latches to high-level output, setting the P23 output latch to low-level
output (Same as in the sample program setting)
PM2
1 1 1
P2
0 0 0
The PM2 register setting value is
is "00000111 (bits 7 to 4 must be set to 0)".
• Assembly language
MOV PM2, #11110000B
MOV P2,
• C language
PM2 = 0b11110000;
P2 = 0b00000111;
24
CHAPTER 4 SETTING METHODS
Figure 4-8. Format of Pull-up Resistor Option Register 2 (PU2)
0 PU23 PU22 PU21
1 0 0 0
0 0 1 1
"11110000
#00000111B
Application Note U18752EJ2V0AN
[Example 2], mentioned later.
PU20
Selection of the P2n (n = 0 to 3) pin internal pull-up resistor
0 Internal pull-up resistor is not connected.
1 Internal pull-up resistor is connected.
0
Selection of the P2n (n = 0 to 3) pin I/O mode
0 Output mode
* In this sample program, P20 to P22 are used as output
ports for lighting LEDs, so port 2 is set as an output port.
1
Selection of the P20 to P22 pin output latch levels
1 High-level output
Selection of the P23 pin output latch level
0 Low-level output
* In this sample program, P20 to P22 are used as output ports
for lighting LEDs, so the P20 to P22 output latch levels are
set to high-level output in the initial settings.
(LEDs are lit when the outputs from P20 to P22 are at low
level (refer to 2.1 Circuit
(bits 7 to 4 must be set to 1)", and the P2 register setting value
Diagram).)