NXP offers a family of 8 I/O and 16 I/O quasi output expanders with different features including reset, interrupt, and EEPROM. The PCF8574 and PCA8575 are well-known general purpose I/O expanders. The PCA9500 is a combination of the PCF8574 with a 2 kilobit EEPROM and the interrupt pin is replaced by the EEPROM write protect (W-P). The PCA9501 is a combination of the PCF8574 with a 2 kilobit EEPROM and the device is offered in a 20-pin TSSOP package. The four extra pins allow the interrupt output to be included in addition to the Write Protect pin. The extra three pins are then used to offer a total of six address pins allowing up to 64 of these devices to share the same I²C bus.