NEC 78K0/KB1+, Preliminary User'S Manual

Page: 79 / 405

CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U16846EJ1V0UD
79
(2) Port registers (P0 to P3, P12, P13)
These registers write the data that is output from the chip when data is output from a port.
If the data is read in the input mode, the pin level is read. If it is read in the output mode, the value of the output
latch is read.
These registers can be set by a 1-bit or 8-bit memory manipulation instruction.
RESET input clears these registers to 00H (but P2 is undefined).
Figure 4-15. Format of Port Register
7
0
Symbol
P0
6
0
5
0
4
0
3
P03
2
P02
1
P01
0
P00
Address
FF00H
After reset
00H (output latch)
R/W
R/W
7
P17 P1
6
P16
5
P15
4
P14
3
P13
2
P12
1
P11
0
P10 FF01H 00H (output latch) R/W
R
7
0 P2
6
0
5
0
4
0
3
P23
2
P22
1
P21
0
P20 FF02H Undefined
7
0
P3
6
0
5
0
4
0
3
P33
2
P32
1
P31
0
P30 FF03H 00H (output latch) R/W
7
0 P12
6
0
5
0
4
0
3
0
2
0
1
0
0
P120 FF0CH 00H (output latch) R/W
7
0
P13
6
0
5
0
4
0
3
0
2
0
1
0
0
P130 FF0DH 00H (output latch) R/W
m = 0 to 3, 12, 13; n = 0 to 7 Pmn
Output data control (in output mode) Input data read (in input mode)
0 Output 0 Input low level
1 Output 1 Input high level