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UCD3138064: Questions about downloading UCD3138064EVM-166 program using pmbus

user4768560
Intellectual 375 points
Part Number: UCD3138064
Other Parts Discussed in Thread: UCD3138

Hi，

When using the UCD3xxx Device GUI software to program the EVM-166, why does the address 11d appear in the log below the software after clicking Scan Device in Rom? Instead of the PMBus address 0x58(88d) previously set in the program? Can you explain in detail?

 I want to connect two UCD3138 PMBUS in parallel,  at this time, how does the UCD3xxx Device GUI software  identify the two UCD3138s?I found that when I click on the command ROM to execute its program, the address of pmbus becomes the pmbus address 0x58 set in the program. I am confused when the UCD3138 is in ROM and its pmbus address is 11d.

With best regards

  • 0
    TI__Expert 4070 points

    Your question has been forwarded to the appropriate engineer.

  • 0
    TI__Genius 17090 points
    You've pretty much figured it out. When the UCD is in ROM mode, it always has an address of 11d. When you download the program, it then has whatever address (and PMBus functionality) the program assigns. This means that if you have two devices in ROM mode on the same bus, you can't differentiate between them.
  • 0 in reply to Ian Bower
    Intellectual 375 points
    Thank you for your answer. Why is the address 11d in ROM mode? What document can I see related to it? Does this depend on the UCD3138\'s peripheral hardware circuitry?

    When I read the UCD3138's user manual, I noticed that there was a section written to ADC00 and ADC01 for pmbus address decoding. But I did not find a description of the purpose of this address decoding. Can you answer this question? Thank you very much!
  • 0 in reply to user4768560
    TI__Genius 17090 points

    We chose the address pretty arbitrarily.  It is fixed because we have low pin count (40) devices, and we didn't want to dedicate any pins to boot ROM modes and limit their use in the final application. 

    If you look at section 13.1.5 in the UCD3138 Technical Reference Manual, you can see the documentation for the address:

    I'm not sure what you mean about the purpose of the address decoding?  It's just a method for setting multiple addresses for devices with minimal external components.