Control Of The I/O Port - Epson E0C6001 Technical Manual

E0C6001 TECHNICAL SOFTWARE
Control of
the I/O port
II-24
The E0C6001 contains a 4-bit general I/O port (4 bits × 1).
This port can be used as an input port or an output port,
according to I/O port control register IOC. When IOC is "0",
the port is set for input, when it is "1", the port is set for
output.
• How to set an input port
Set "0" in the I/O port control register (D0 of address 0FCH),
and the I/O port is set as an input port. The state of the I/O
port (P00–P03) is decided by the data of address 0F6H. (In
the input mode, the port level is read directly.)
• How to set an output port
Set "1" in the I/O port control register, and the I/O port is
set as an output port. The state of the I/O port is decided by
the data of address 0F6H. This data is held by the register,
and can be set regardless of the contents of the I/O control
register. (The data can be set whether P00 to P03 ports are
input ports or output ports.)
The I/O control registers are cleared to "0" (input/output
ports are set as input ports), and the data registers are also
cleared to "0" after an initial reset.