Step 1: For the DS90UB633A/662
FPD-Link III chipset, BIST mode is enabled via the BISTEN pin of DS90UB662-Q1 FPD-Link III
deserializer. The desired clock source is selected through the deserializer GPIO0 and
GPIO1 pins as shown in Table 7-4.
Step 2:DS90UB633A-Q1 serializer BIST pattern is enabled
through the back channel. The BIST pattern is sent through the FPD-Link III to the
deserializer. Once the serializer and deserializer are in the BIST mode and the
deserializer acquires lock, the PASS pin of the deserializer goes high, and BIST starts
checking the FPD-Link III serial stream. If an error in the payload is detected, the PASS
pin switches low for one half of the clock period. During the BIST test, the PASS output
can be monitored and counted to determine the payload error rate.
Step 3: To stop the BIST mode, the
deserializer BISTEN pin is set LOW. The deserializer stops checking the data. The final
test result is not maintained on the PASS pin. To monitor the BIST status, check the BIST
Error Count register, 0x57 on the deserializer.
Step 4: The link returns to normal
operation after the deserializer BISTEN pin is low. Figure 7-8 shows the waveform diagram of a typical BIST test for two cases. Case 1
is error free, and Case 2 shows one with multiple errors. In most cases, it is difficult
to generate errors due to the robustness of the link (differential data transmission,
etc.); thus, they may be introduced by greatly extending the cable length, faulting the
interconnect, or by reducing signal condition enhancements (Rx equalization).