Teledyne LeCroy QPHY-HDMI - Manual (Page 22)

Test7-6: TMDS Inter-Pair Skew
This test confirms that that any skew between the differential pairs in the TMDS portion of the
HDMI link does not exceed the limits in the specification.
R EQUIREMENT
Inter-pair skew must not exceed 0.20*TPIXEL.
Reference: [HDMI: Table 4-16] Source AC Characteristics at TP1
M ETHODOLOGY
1. Connect TPA-P adapter to Source DUT HDMI output connector.
2. Connect the first TF-HDMI-3.3V to TMDS_DATA0.
3. Connect the second TF-HDMI-3.3V to TMDS_DATA1.
4. Configure Source DUT to output an HDMI signal with a video format and pixel size with
highest supported TMDS clock frequency.
5. Capture (trigger) or find a sequence of Control Period encoded characters. Either 10-bit
or 20-bit trigger may be used. For 10-bit trigger:
6. Find the first bit of the TMDS character on the two TMDS channels. The CTL encoding
pattern 1101010100 corresponds to:
a. TMDS_DATA0: HSYNC=1, VSYNC=0
b. TMDS_DATA1: CTL0=1, CTL1=0 (any Preamble)
c. TMDS_DATA2: CTL2=1, CTL3=0 (Data Island Preamble)
If it is difficult to capture using the above patterns, then any of the following (Control
Period) patterns may be used:
a. 0010101011
b. 1101010100
c. 0010101010
d. 1101010101
7. Examine second channel for any valid CTL code and measure TIPSKEW between
channels.
8. For 20-bit trigger, find the first bit of the following 20-bit sequence on the TMDS
channels.
a. For Channel 0: 0010101011 0011001101
b. For Channel 0: 0010101010 0011001101
c. For Channel 0: 1101010101 0011001101
d. For Channel 1: 0010101010 1100110010
e. For Channel 2: 0010101011 0011001101
9. Examine second channel for the appropriate sequence and measure TIPSKEW between
channels. If TSKEW > 0.2*TCHARACTER then FAIL.
10. Repeat the test for remaining combinations of TMDS_DATAx pairs.
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