Let me ask about TMDSFREQ[8:0],TMDSFREQ_FRAC[6:0] of ADV7619.
How does ADV7619 measure TMDS frequency?
Does it use XTAL?
I would like to know accuracy of the read back value.
With best regards.
Have you gone through the UG-237 Hardware User Guide? In this document there is an section talking about TMDS Measurement. I hope this would surely help you. Please check the below link.
Thank you for your reply.
Of course, I have already checked UG-237. But I am not sure how to measure TMDS frequency.
I would like to know the way how ADV7619 get the TMDS frequency value.
(For example, ADV7619 counts the width of TMDS clock x 128 by XTAL clock)
Thank you for your cooperation.
Could you tell me this status?
I do not know answer for this.
Experts will provide answer for this.
Looking at UG-237, Table 50. From the CHx_BL, CHx_LCF, CHx_LCVS and knowledge or XTAL you can define which standard the input is. Once you know the standard, by definition you know the TMDS frequency. For instance if I know the standard is 720p (regardless of 50 or 60 Hz) you know the TMDS clock = 74.25MHz.
In other words the TMDS clock is not directly related to the XTAL frequency but a derived value from values that are measured from the XTAL clock. Also CHx_BL is the only variable derived directly from counting XTAL clocks.
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