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Original question:

DP83867CR: Multiple OPMODE selection (JTAG and RGMII to 1000Base-X)

DP83869HM: DP83869HM JTAG mode issue

Maxim Danchenko
Prodigy 20 points

Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869EVM

Tool/software:

Hello

We have tried to setup "JTAG for boundary scan" mode on DP83869HM PHY with resistors, as described in datasheet

When the device in JTAG mode, we can not access it using MDIO interface.

Also we have noticed, that when PHY is in JTAG mode, the state of INT_N/PWDN_N pin is low.

If we change initial setup with resistors to RGMII to 1000Base-X mode, then we can communicate with DP83869HM using MDIO interface.

Question:

  1. is JTAG mode on this device is a normal working mode, or it is used only if factory,
  2. should we have access to PHY through MDIO interface when it in JTAG mode, 
  3. what we should do to change mode from JTAG to RGMII to 1000Base-X, when by default resistors are soldered to enable PHY in JTAG mode?

Thanks in advance

Maxim. 

  • 0
    TI__Mastermind 19621 points

    Hi Maxim,

    This is an excellent question, based off what I know of JTAG I would expect the PHY to not function. To confirm I went into lab with DP83869EVM to see if I could read registers.

    1. is JTAG mode on this device is a normal working mode, or it is used only if factory
      1. It is not a normal working mode. The device will not be functional
    2. should we have access to PHY through MDIO interface when it in JTAG mode
      1. In my experiment, when strapped into OPMODE '111', no register access was possible
    3. what we should do to change mode from JTAG to RGMII to 1000Base-X, when by default resistors are soldered to enable PHY in JTAG mode?
      1. The only way would be to change the strap resistors, since Register access is unavailable.

    Regards,

    Alvaro