The LTC1329 can communicate with external circuitry by using one of three interface modes: standard 3-wire serial mode and two pulse modes. Upon power-up, the internal counter resets to 1000 0000B, the DAC output assumes midrange and the chip is configured in 3-wire or pulse mode depending on the signal level at CS. In 3-wire mode, the system MPU can serially transfer 8-bit data to and from the LTC1329. In pulse mode, the upper six bits of the DAC output can be programmed for increment-only (1-wire interface) or increment/decrement (2-wire interface) operation depending on the signal level at DIN.