The MCP23S09-E/MG is an 8-bit I/O Expander with open-drain outputs. It consists of multiple 8-bit configuration registers for input, output and polarity selection. The system master can enable I/Os as either inputs or outputs by writing 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 interrupt capture register captures port values at the time of the interrupt, thereby saving the condition that caused the interrupt. The power-on reset (POR) sets the registers to their default values and initializes the device state machine. The hardware address pin is used to determine the device address.
Open-drain outputs
Configurable as active-high, active-low or open-drain
Interrupt-on-change from configured defaults or pin change
Polarity inversion register to configure the polarity of the input port data
