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Original question:

[FAQ] DS90UB953-Q1: Latency of DS90UB953-Q1 and DS90UB954-Q1

DS90UB953-Q1: latency counting

YU-CHANG LIANG
Prodigy 20 points
Part Number: DS90UB953-Q1

Tool/software:

 dear ti team 

I just saw the comment "954, the latency is dominated by the line buffer in the 954. Other latency from 953 serialization and prop delay through the cable are small compared to the 954 line buffer time. 

The 954 buffers up to 2 lines from each RX port, so the latency can be roughly equated as 2x the line time. 

Ex. For 1280x800 @ 60Hz, the video line time is ~20.1us:

So total buffer time would be ~40.2us which roughly equals the total latency through the 953/954 chain. "

I want confirm that when the whole image has been sent, it should take  800/2 times 40.2us = 400*40.2us= 16080us= 1.6ms 

  • +1
    TI__Mastermind 28340 points

    Hello Yu-Chang,

    The table shown is an example of the horizontal timing from a specific video stream. Different video streams with different resolutions would have different line periods.

    In this example, the worst-case latency would be when each line stays in the buffer for x2 the line period. That means the worst-case latency across an entire frame in this example will be 800 x 40.2us = 32ms

    However, it is unlikely to reach this point as our Des device is continuously pulling lines of video data from the RX Port line buffer to output. The best case latency across the entire frame would be 800 x 20.1us = 16ms, where each line of video data is immediately pulled from the RX Port as they arrive.

    Best,

    Justin Phan