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When the input/output port is set to input (PnmDIR=1), a level that was input to the port pin is read from the data register (PnmD). Therefore, it looks that write to the data register is ignored. However, the data register value will be changed to the written value when the PnmDIR register is set to output (PnmDIR=0) because the written value actually remains in the data register.