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PCM2704C: When HID function is not used, what is DAC default code at power on?

Kazuya Nakai59
Guru 20430 points
Part Number: PCM2704C
Other Parts Discussed in Thread: HID2, PCM2706

Hello guys,

One of my customers is drawing a schematic to evaluate PCM2704C for their new products.
They have the following questions. Could you please give me your reply for them?

Q1. They don't need HID control function(mute, volume up, volume down). So they are going to leave HID0~HID2 (Pin No,22~24) open.  
      Is it no problem? Or are these pins needed to connected to GND when HID control is not needed?

Q2. When HID function is not used, what is DAC default code at power on?

Your reply would be much appreciated.

Best regards,

Kazuya. 

 
      

  • 0
    TI__Mastermind 20850 points

    Hello Kazuya-san

    The PCM2704C has 3 external interrupts (HID) which control the Mute, Volume Up, and Volume Down; these control inputs are active High. So you can ground them if not planning to use them.

    Interface number 2 can report these three key statuses for any model. These statuses can be set by the HID0 through HID2 pins 

    • Mute (0xE2) • Volume up (0xE9) • Volume down (0xEA). So you should be able to read these registers to see the values written; my guess is they all read 0.

    Kind Regards,

    Arash

  • 0 in reply to Arash Loloee
    Guru 20430 points

    Hello Arash,

    Thank you very much for your prompt reply.
    Could I ask you the following additional questions?

    Q1. For example, "HID key state input (volume up), active HIGH (PCM2706). MC input (PCM2707) (2)"  is described
           in DAC2704C datasheet as HID1/MC function explanation on page 4.
           Also I checked the device EVM user's guide on the following URL.
           https://www.ti.com/lit/ug/sleu114/sleu114.pdf?ts=1655244576520

          I found that HID0~2 pins are pulled up to /SSPND pin in EVM schematic on page 4.

          My question is the follow.
          Is "active high" applied for PCM2706 only because the pin description says "active HIGH (PCM2706)"

    Q2. Is there any document or information that says what the default code is because they don't have the device EVM now and they can't read out the data.

    Thank you again and best regards,

    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 20850 points

    Hello Kazuya,

    The ~SSPN is a flag pin. If there is no error, ~SSPN is high and thus HID pins are pulled high and thus functioning. Once there is an error, ~SSPN will go LOW and thus HUD will pull low as well and stop.

    regarding documents, these are very mature parts and unfortunately  there is not much documentation available that I can refer you to it.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Guru 20430 points

    Hello Arash,

    Thank you very much for your reply. 

    I understood why HID0~2 were connected to ~SSPN. 

    Could I ask you an additional question in other word as the below?

    Q. Does DAC2704C have default code for volume data? 

        Is the answer TI doesn't know whether the device has a default code for volume
        because DAC2704C is very old device?

    Thank you again and best regards,

    Kazuya.

  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 20850 points

    Hello Kazuya, Yes, These are very old parts and thus not much documentation are around to find. So I don't know if there is a default code for volume . 

    Thank you,

    Arash

  • 0 in reply to Arash Loloee
    Guru 20430 points

    Hello Arash,

    Thank you very much for your reply and I'm sorry to be late response.

    I understood it and I will recommend the customer to take any countermeasure because the device default code has been unknown.

    Thank you again and best regards,

    Kazuya.