DVI Compliance Testing

DVI specification enforces developers to comply with several stringent compliance tests for DVI designs. Compliance testing is a challenge if it needs human intervention. The human intervention makes testing difficult and slows the test process. The DVI transmitter eye-masks (TP2) are normalized and change dynamically with the V_swing and T_bit values, while the cable and receiver masks (TP3) are normalized in time and change according to the changes in T_bit value of the signal. This makes manual testing subjective and error prone.

Compliance testing is conducted for transmitter, cable and receiver at various test points as shown in the Fig.2. These test points are defined to be the contact point between the mated connected pairs of the cable assembly.

Fig. 2

Test fixture or breakout boards are required to probe the various test points (TP2 and TP3).

The test fixture shown below the Fig.3 is available from Digital Data Working Group (DDWG) and the test fixture shown in the Fig.4 is available from Silicon Image.

Figure 3

Figure 4

Automated testing based on objective pass/fail detection without human intervention helps to achieve the time-to-market goals. The results are obtained quickly and are more dependable.

TDSDVI test software dramatically enhances productivity.

Pre-requisite to Compliance testing - Tbit calculation

One unit interval of the DVI signal is referred to as T_bit. The DVI Test and Measurement guide recommends Tbit calculation to be performed on the transmitter (differential) clock.

T_bit calculation needs to be performed before conducting any tests using TDSDVI. The user needs to connect the transmitter clock to one of the channels of the oscilloscope and perform T_bit calculation.

Correct T_bit value is very essential for calculating the limit values. Hence, it is recommended to always conduct T_bit calculation whenever there is a change in the system configuration.