a mixed signal integrated circuit device , e . g ., digital - to - analog converter , has a serial interface communication protocol that accesses volatile and / or non - volatile memory and allows a preprogrammed output voltage whenever the mixed signal device is powered - up . however , unlike conventional dacs , dacs with non - volatile memory may need special interface communication protocols for effective operation of the dac and communications between a system master controller unit . interface communications protocols that do not violate standard serial bus communications protocols are provided for communicating between the volatile and non - volatile memories of the dac so that the mcu may access the dac &# 39 ; s memories . the mixed signal integrated circuit device has a user programmable address .