• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 62 subscribers
  • Views 613 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCD9081 detected at unexpected address

Chetan Maheshwari
Prodigy 190 points
Other Parts Discussed in Thread: UCD9081

Hi,

We are using UCD9081 to enable & monitor rail voltages. There are 2 boards with same I2C bus running across a backplane. For 1stdevice addressing we used pullups on all 4 address pins so that the device gets detected at address 0x6F and for the second board addressing is coded to so as to have that device at (0x6E)

When the UCD9081 GUI is started the boards get restarted & the device is detected at expected address (0x6F & 0x6E).

After a power cycle, while reading through my software application running on FPGA, the devices are detected at address 0x60 which is unexpected address for any of the two boards. If I reset the device by writing to restart register ((0x2F) a value 0x00),the boards get restarted and the device is now detected at address (0x60 & 0x6E) through software.The behavior is same if I reverse the position of the boards w.r.t the backplane.

We have Power on reset TPS3825-33DBVT IC from TI, with its RESETn output connected to RSTn pin of UCD. 

Please let me know why UCD9081 device is not sampling address pins just after a power cycle?How is that both the devices are getting detected at same address after a power cycle. Also why only one device gets detected at correct address while the other one is detected at unexpected address after writing to restart register.

  • 0
    TI__Genius 13700 points

    The address pins are multifunction and can be GPIO (and for ADDR1 also an Enable) as well as ADDR inputs.   During reset (power cycle/re-start) have you monitored the ADDRx pins to determine what state they are in?

    When you say the behavior is the same when reversing the position of the boards in the backplane, do you mean the problem follows one board or you get the same error in the same position with both boards?

     

  • 0 in reply to Brad
    Prodigy 190 points

    Hi Brad,

    The device is a QFN package, its difficult to monitor ADDRx pins.

    The problem is same even when reversing the board positions. All ADDRx pins on both both are pulled upto to 3.3V by 4.7kohm resistor. Address settings are done by pulling those pins low by 0ohm resistor. (The board is 6U VPX standard and GA pins are used to set ADDRx pins). 

    There are 3 slots for inserting the boards. 2 slots can take board of type 'A'. We have set the ADDRx pins of these boards as '0xF' & '0xE'. 1 slot can take board of type 'B'. ADDRx pins are set as '0x8' for this slot. When I insert 2 boards of type 'A', address conflict occurs when they are powered on. But after giving reset to the device one of the two addresses are taken correctly while the other is still '0x0'.