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Interference when input pins & output pins are mixed w/ output pin side?

Latest Updated:12/01/2011

Question:

In the uPD780308, when input pins and output pins are mixed in the same port and the on-chip pull-up resistor is set to ON, does this cause interference with the output pin side?

Answer:

No, this does not cause interference. (There is no problem.)
As can be seen in the port block diagram, the pull-up resistor of each port can only be enabled by setting the PUO register to 1 and also setting the PM register to 1 (in other words, input port mode).
Therefore, no pull-up resistor can be connected to a pin specified as output.
Suitable Products
RL78 Family
78K Family