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LMH1983 oparetion

hisakichi kobayashi
Intellectual 950 points
Other Parts Discussed in Thread: LMH1983

Hi all.

There is a question of LMH1983.

To the table of Audio FORMAT detection code, It is checking that four sorts of word clocks are published.
To Support Format Lookup Table of Table.1 Since only two sorts were published, it checked.
Are they four sorts of 32k,44.1k,48k,96kHz? (Word clock)

At the time of a word clock input, Although the signal was outputted TOF2 and TOF3, TOF1 did not output.
Is it normal now?  (Three TOF are made a setup of output enabling. )

In addition.
There is a question about the HOLDOVER operation at the time of a reference input being lost.

In resister 05h is 2Bh (default) and 18h is 01h (default) and 19h is FFh (default),
Although the 1Ah is 00h (default) and 1Bh is 01 h (default) oparate it,

In this state, when a reference input is lost, it goes into HOLDOVER operation,

The error output voltage of PLL1 should keep the error output voltage at the time of there being a reference input.
However, error voltage will not be kept if actual operation on an evaluation board cuts the input of a reference,
It will change on unfixed voltage.

Why doesn't it carry out normal HOLDOVER operation?

Best Regerds,
Hisa Kobayashi.

  • 0
    TI__Expert 4400 points

    We are looking into this for you and will respond shortly.

    Gary Melchior

  • 0 in reply to Gary Melchior
    TI__Guru* 93670 points

    Kobayashi-San,

    1). Audio Auto Format Detection:

    Auto format detection recognizez only 4 audio format(48KHz, 96KHz, 44.1KHz, and 32KHz). These are the only formats that would be recognized by the auto format detection. If we detect one of these formats then the other TOF outputs would be disabled since the incoming frame format does not comply with other video format that enables the other TOF signals.

    2). Hold over Mode:

    Once we lose the reference we should be able to maintain our phase/frequency lock(once the reference is removed). Perhaps maybe when they are removing the reference there are some un-wanted sync pulses that could be confusing the LMH1983. If this is the case, perhaps once we sense NO_REF we can put the device in never_align mode.

    Regards,,nasser

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Intellectual 950 points

    Hi nasser-san

    Thank you for the reply.  Both replies have improved.

    Regard,

    Hisakichi Kobayashi.