TEXAS INSTRUMENTS PCA9536D .

The PCA9536D is a remote 4-bit I²C and SMBus I/O Expander with configuration registers designed for VCC operation. It provides general-purpose remote I/O expansion for most microcontroller families via the I²C interface (serial clock (SCL), serial data (SDA)). The PCA9536 features 4-bit configuration (input or output selection), input port, output port and polarity inversion (active high or active low) registers. At power on, the I/Os are configured as inputs with a weak pull up to VCC. However, the system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. If no signals are applied externally to the PCA9536, the voltage level is 1 or high, because of the internal pull up resistors. The data for each input or output is stored in the corresponding input port or output port 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.