3822 datasheet(68/328 Pages) RENESAS

68 / 328 page

APPLICATION

2.1 I/O pins

3822 GROUP USER’S MANUAL

2–2

2.1 I/O pins

2.1.1 I/O ports

(1) I/O port write and read

sThe input-only ports and programmable I/O ports set for the input mode

The input-only ports and the programmable I/O ports set for the input mode are floating. The value

(pin state) input to the port is read by reading the port register corresponding to each port.

In writing data into the port register corresponding to each port, the data is only written to the port

sOutput-only ports and programmable I/O ports set for the output mode

The value written to the port register corresponding to an output port or a programmable I/O port set

for the output mode is output externally through a transistor.

In reading the data of the port transistor corresponding to each port, the pin state is not read but the

value written to the port register is read. Accordingly, even if the output “H” voltage is reduced or the

output “L” voltage is increased by external load, the previous output value is correctly read.

Fig. 2.1.1 I/O port write and read

At output : •An output value is set by writing to the

port register.

Port register

(at writing)

At input : •Writing to a port register is possible.

V : The P- and N-channel transistors are cut off.

Port register

(at reading)

Port direction

registerV

(“0”)

Read the pin state

Port

Port direction

(“1”)

“H” level output

“L” level output

•A pin state is read by reading the

port register.

•Reading a port register is possible.

3822 Datasheet(PDF) 68 Page - Renesas Technology Corp