Programming Comparator

Programmable Levels

You can program the comparator with the following pin levels using the NI-Digital Pattern Driver or set pin levels interactively in the Digital Pattern Editor. Pin levels are programmable per pin or by pin group.

V_OL—Specifies the DUT output voltage below which the comparator on the instrument pin interprets a logic low (L).

V_OH—Specifies the DUT output voltage above which the comparator on the instrument pin interprets a logic high (H).

The NI-Digital Pattern Driver does not enforce a minimum separation between V_OH and V_OL. Refer to PXIe-6570 Specifications for information about the minimum separation required for accurate results.

Data States Comparison

For each pin in the current vector, the comparator evaluates the output voltage of the DUT (V_OUT) against the currently specified V_OH and V_OL levels at the compare strobe time. This evaluation is performed for each pin that specifies one of the following data states:

• L—Compare low. Expect V_OUT < V_OL.
• H—Compare high. Expect V_OUT > V_OH.
• V—Compare valid. Expect V_OUT > V_OH or V_OUT < V_OL.
• M—Compare midband. Expect V_OL < V_OUT < V_OH.

If the evaluation of any pin does not match its expected value, the comparator generates a failure for that cycle. Use the match opcode to modify this behavior and does not generate a failure for that cycle.