The PCA9534A consists of one 8-bit configuration (input or output selection), input port, output port, and polarity inversion (active high or active low) register. At power on, the I/Os are configured as inputs. However, the system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the input port register can be inverted with the polarity inversion register. All registers can be read by the system master. The system master can reset the PCA9534A in the event of a timeout or other improper operation by utilizing the power-on reset feature, which puts the registers in their default state and initializes the I2C/SMBus state machine. The PCA9534A open-drain interrupt (INT) output is activated when any input state differs from its corresponding input port register state and is used to indicate to the system master that an input state has changed. 1