Question: how to measure voh and vol?
Answer: Step 1: Power the DUT by applying VDD ...  Step 2: Condition the DUT outputs to the logic-high state. ...  Step 3: Set the SMU to sink a small current (VOH), or source a small current (VOL) ...  Step 4: Connect the DUT pin to be tested. ...  Step 5: Measure the output voltage. ...  Step 6: Switch to the next pin and repeat.