The DIO enables the 8-bit DAC and generates the clock (Clk) as the data strobe. Since the DIO and the UUT share the same data bus, the DIO signals to the UUT that it is ready to RUN. The UUT controls when the DIO run and when break out of the program.
The DIO generates a Master Clear (MC), active low, to initialize the DAC and the LBC upon startup. It also switches the data lines (D0-D7) between Tri-State to active when the DIO is in RUN. Since it’s critical for the UUT not to have conflicts on the data bus, a low on the OutEn line will signal to the LBC that the data bus is now occupied by the DIO.
When the DIO is ready to run, the BusReq is set to low and the DIO is ARMed. When the LBC is able to grant access to the DIO, it responds by lowering BusAv, which in return triggers the DIO to run state.
Depending on the selected waveform (Wvfm), the DIO generates one of two signals: a saw or a triangular wave.
The UUT can terminate the program at any time by lowering the Stop line.