2 Test Setup and Procedure

The cable break test is designed to check if a link down is recognized after a disruption purposefully casued by the break machine, and if a link up is recognized after the disruption is cleared. DP83822 is connected to a break machine using a cable of varied length. The break machine is connected to a link partner with a cable that is always 1 meter. Figure 2-1 shows the cable break test setup. The test described in this app note is conducted with cable length up to 140 m. However, any length of cable can be used depending on the requirements of the application.

Figure 2-1 Cable Break Test Setup

The break machine is capable of either breaking or shorting any combination of 4 wires and the shield for a total of 32 different breaks and shorts. When a break or short executes, both the DP83822 and link partner should recognize a link down. This disruption is active for 2 seconds. After the two seconds, the break or short is withdrawn, and both PHYs should recognize a link up and packets will be transmitted. This process was repeated 500 times for each of the 32 disruption combinations.

Figure 2-2 shows an example of a break scenario that was covered during the test. In the figure, wire 1 and wire 6 were broken.

Figure 2-2 Wire 1 and 6 Break Scenario

Figure 2-3 shows an example of a short scenario that was covered during the test. In the figure, wire 1, 2, and 3 were shorted together.

Figure 2-3 Wire 1, 2, and 3 Short Scenario