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UCD90120A: Reconfigure PMBus address in Fusion GUI.

Yee Yong Teo
Expert 4335 points
Part Number: UCD90120A

Hi,

I created a project with address 104d. Then I would like to change it to 126d. I click on build system->modify existing system. But I couldn't find the 126d in the address list anymore. Any idea?

Thanks.

- YY

  • 0
    TI__Guru 66230 points

    hi YY

    Why do you want to use 126? address 126 is a special address to enable the JTAG. Please refer 120A DS to see how to force the device into 126 address.

    Regards

    Yihe

  • 0 in reply to yihe
    TI__Expert 4335 points

    Hi Yihe,

    Because I want to use Fusion + JTAG to program the device. In this case, I need to change the address to 126d, right?

    Thanks.

    - YY

  • 0 in reply to Yee Yong Teo
    TI__Guru 66230 points
    YY
    Not necessarly. also having a project file with address 126 does not help you to enable JTAG.

    The JTAG interface can provide an alternate interface for programming the device. It is disabled by default in
    order to enable the GPIO pins with which it is multiplexed. There are two conditions under which the JTAG
    interface is enabled:
    • On power-up if the data flash is blank, allowing JTAG to be used for writing the configuration parameters to a
    programmed device with no PMBus interaction
    • When address 126 (0x7E) is detected at power up. A short to ground or an open condition on either address
    pin will cause an address 126 (0x7E) to be generated which enables JTAG mode.

    Regards

    Yihe
  • 0 in reply to yihe
    TI__Expert 4335 points
    Hi Yihe,

    Understood about how to enable the JTAG. But for my case, how do I write new configuration with address 104d using TI Fusion? I need to change he PMBUS address to 126d on both hardware & software, right? If yes, how do I change it in TI Fusion software?

    Thanks.

    - YY
  • 0 in reply to Yee Yong Teo
    TI__Genius 13700 points

    1)  There is no association between the address 126 and JTAG other than they both occur when powering up an uncofigured UCD device.  The address is not used as part of downloading the configuration via JTAG.

    2)  The address selection within the Fusion GUI is provided as a conviencience for the designer to track which device they are working on but it is not actually required to match the address of the device to which it will be written.

    3)  The association between project file and device occurs during the actual download process.

    4)  The final address of each UCD device will be determined by the hardwired resistors on the address pins not by the address in the project file.