1. A digitally programmable array-based electronic chip for carrying out biological reactions in response to electrical stimuli, comprising: an array of electrode sites, each electrode site including a sample-and-hold circuit coupled to a working electrode; a plurality of switches for selectively coupling the working electrodes to the output of a digital-to-analog converter (DAC); a control logic module coupled to the DAC and the plurality of switches; and an external processor that digitally interfaces with the control logic module, wherein the communication between the control logic and the external processor includes a clock signal, a data in signal, and a data out signal.