PCA9501PW 8-Bit I/O Expander NXP Semiconductors PCA9501PW 8-bit I/O Expander is with an onboard 2-kbit EEPROM. The PCA9501PW features I/O expandable eight quasi-bidirectional data pins that can be independently assigned as inputs or outputs to monitor the board-level status or activate indicator devices such as LEDs. The system master writes to the I/O configuration bits in the same way as for the PCF8574. The EEPROM on the NXP Semiconductors PCA9501PW can be used to store error codes or board manufacturing data for read-back by application software for diagnostic purposes and are included in the I/O expander package. The PCA9501PW is ideal for a variety of applications, including board version tracking and configuration, board health monitoring and status reporting, and more.