Method for digital bus testing
View Patent ↗An interface for a bus test instrument is readily adaptable for testing a wide range of bus types. The interface includes a pair of transmit lines and a pair of receive lines. A transmitting circuit is adaptable for transmitting either single-ended or differential signals over the transmit lines, and at least one receiving circuit is adaptable for receiving either single-ended or differential signals from either the receive lines or the transmit lines. The flexible interface allows the testing of single-ended and differential busses, as well as busses that support both unidirectional and bidirectional communication.
1. A method for testing digital busses, comprising:
connecting a device under test to at least four nodes in a test interface circuit, the test interface circuit having a controller, a first transmitter coupled to a first node, a second transmitter coupled to a second node, a first receiver, and a second receiver;
selectively configuring the first transmitter, second transmitter, first receiver and second receiver to a prescribed configuration by
selectively coupling the first receiver to either a third node or the first node; and
selectively coupling the second receiver to either a fourth node or the second node;
selectively driving the first node and the second node to one or more programmable drive levels;
comparing inputs of the first receiver and the second receiver to one or more programmable thresholds.
2. The method of claim 1 wherein the step of selectively configuring further comprise:
configuring the first transmitter and the second transmitter as two unidirectional single-ended transmitters adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as two unidirectional single-ended receivers adapted to compare their respective input signals with at least one programmable threshold.
3. The method of claim 1 wherein the step of selectively configuring further comprise:
configuring the first transmitter and the second transmitter as two unidirectional single-ended transmitters adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as one unidirectional differential receiver adapted to compare a differential input to at least one programmable threshold.
4. The method of claim 1 wherein the step of selectively configuring further comprises:
configuring the first transmitter and the second transmitter as one unidirectional differential transmitter adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as two unidirectional single-ended receivers adapted to compare their respective input signals with at least one programmable threshold.
5. The method of claim 1 wherein the step of selectively configuring further comprises:
configuring the first transmitter and the second transmitter as one unidirectional differential transmitter adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as one unidirectional differential receiver adapted to compare a differential input to at least one programmable threshold.
6. The method of claim 1 wherein the step of selectively configuring further comprises:
configuring the first transmitter and the second transmitter as two bi-directional single-ended transmitters adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as two bi-directional single-ended receivers adapted to compare the respective inputs to at least one programmable threshold.
7. The method of claim 1 wherein the step of selectively configuring further comprises:
configuring the first transmitter and the second transmitter as one bi-directional differential transmitter adapted to drive the respective nodes to at least two programmable drive levels; and
configuring the first receiver and second receiver as one bi-directional differential receiver adapted to compare a differential inputs to at least one programmable threshold.
8. The method of claim 1 wherein the first transmitter and the second transmitter are tri-statable.
9. The method of claim 1 wherein the step of selectively driving further comprises the step of adjusting a slew rate of transmitted signals to a prescribed slew rate.