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CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (I/O Ports)
4.6.3 I/O control registers and input/output mode
Input or output mode can be set for the I/O ports by writing data into the corresponding I/O control
registers IOCxx.
To set the input mode, write "0" to the I/O control register. When an I/O port is set to input mode, it
becomes high impedance status and works as an input port.
However, when the pull-up explained in the following section has been set by software, the input line is
pulled up only during this input mode (except for P40–P43).
To set the output mode, write "1" is to the I/O control register. When an I/O port is set to output mode , it
works as an output port, it outputs a high level (V
) when the port output data is "1", and a low level
DD
(V
) when the port output data is "0".
SS
If perform the read out in each mode; when output mode, the register value is read out, and when input
mode, the port value is read out.
At initial reset, the I/O control registers are set to "0", and the I/O ports enter the input mode.
The I/O control registers of the ports that are set as input/output for the serial interface and A/D
converter can be used as general purpose registers that do not affect the I/O control. (See Table 4.6.1.1.)
4.6.4 Pull-up during input mode
A pull-up resistor that operates during the input mode is built into the I/O ports P10–P13, P20–P23 and
P30–P33 of the S1C6P366.
The pull-up resistor becomes effective by writing "1" to the pull-up control register PULxx that corre-
sponds to each port, and the input line is pulled up during the input mode. When "0" has been written,
no pull-up is done.
At initial reset, the pull-up control registers are set to "1".
The pull-up control registers of the ports, that are set as input/output for the serial interface, can be used
as general purpose registers that do not affect the pull-up control. (See Table 4.6.1.1.)
The pull-up control registers of the port, that are set as input for the serial interface, function the same as
the I/O port.
EPSON
S1C6P366 TECHNICAL MANUAL
41
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