DS90UB929-Q1 Datasheet, PDF (25/71 Pages) Texas Instruments – 720p HDMI to FPD-Link III Bridge Serializer

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DS90UB929-Q1
SNLS457 – NOVEMBER 2014
Step 4: The link returns to normal operation after the deserializer BISTEN pin is low. Figure 15 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
medium, or reducing signal condition enhancements (Rx Equalization).
Normal
Step 1: DES in BIST
BIST
Wait
Step 2: Wait, SER in BIST
BIST
start
Step 3: DES in Normal
Mode - check PASS
BIST
stop
Step 4: DES/SER in Normal
Figure 14. BIST Mode Flow Diagram
8.3.17.2 Forward Channel And Back Channel Error Checking
While in BIST mode, the serializer stops sampling the FPD-Link input pins and switches over to an internal all
zeroes pattern. The internal all-zeroes pattern goes through scrambler, DC-balancing, etc. and is transmitted
over the serial link to the deserializer. The deserializer, on locking to the serial stream, compares the recovered
serial stream with all-zeroes and records any errors in status registers. Errors are also dynamically reported on
the PASS pin of the deserializer.
The back-channel data is checked for CRC errors once the serializer locks onto the back-channel serial stream,
as indicated by link detect status (register bit 0x0C[0] - Table 8). CRC errors are recorded in an 8-bit register in
the deserializer. The register is cleared when the serializer enters BIST mode. As soon as the serializer enters
BIST mode, the functional mode CRC register starts recording any back channel CRC errors. The BIST mode
CRC error register is active in BIST mode only and keeps a record of the last BIST run until cleared or the
serializer enters BIST mode again.
BISTEN
(DES)
TxCLKOUT±
TxOUT[3:0]±
DATA
(internal)
PASS
Prior Result
PASS
DATA
X
(internal)
PASS Prior Result
Normal
PRBS
X = bit error(s)
X
X
BIST Test
BIST Duration
FAIL
BIST
Result
Held
Normal
Figure 15. BIST Waveforms, in Conjunction with Deserializer Signals
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