GMS81508A Datasheet, PDF (53/91 Pages) Hynix Semiconductor – USERS MANUAL

HYUNDAI MicroElectronics
3. I/O PORTS
There are 7-ports(R0~R6) in this device. This ports are double-functional ports and the function can
be selected by program.
The direction of ports is determined by Port Direction Register.(1=output, 0=input) The data that is
written on the programmed output pin is stored in the port data register and is transferred to the
output pin. When data is input to the programmed pin. data is read not from output pin but from port
data register. therefore, previously output data can be read correctly regardless or the logical level
of the pin due to output loading.
Because the programmed input pin is floating, the value of the pin can be read correctly. When
data is written to the programmed input pin, it is written only to the port data register and the pin
remains floating.
3.1. R0 PORT
R0 Port is composed of 8-bit programmable I/O pin.
Register Name
R0 I/O Direction Register
R0 PORT Data Register
Symbol
R0DD
R0
R/W
W
R/W
Address
00C1_H
00C0_H
Initial Value
0000 0000
Not initialized

R0 PORT I/O DIRECTION REGISTER
R0DD
<00C1_H>
W
W
W
W
W
W
W
W
7
6
5
4
3
2
1
0
R0DD7 R0DD6 R0DD5 R0DD4 R0DD3 R0DD2 R0DD1 R0DD0

R0 PORT DATA REGISTER
Determines I/O of R0 port
0 : Input
1 : Output
R0
<00C0_H>
R/W R/W R/W R/W R/W R/W R/W R/W
7
6
5
4
3
2
1
0
R07 R06 R05 R04 R03 R02 R01 R00
Port R0 output data
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