intersil X9279 Single Supply/Low Power/256-Tap/2-Wire Bus handbook
Datasheet
The X9279 is a single supply/low power/256-tap/2-wire bus single digitally controlled potentiometer. It features 256 resistor taps and a 2-wire serial interface for write, read, and transfer operations. The device has nonvolatile storage of multiple wiper positions for each potentiometer, power-on recall, low standby current, and high data retention capability.