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TM4C1294KCPDT: XDS110 connection error with new board design

Peter Jaquiery
Intellectual 635 points
Part Number: TM4C1294KCPDT

Tool/software:

We are bringing up a new board and are not able to get the debug probe to connect. From CCS we get an error dialog with the text:

Error connecting to the target:
(Error -2062 @ 0x0)
Unable to halt device. Reset the device, and retry the operation. If error persists, confirm configuration, power-cycle the board, and/or try more reliable JTAG settings (e.g. lower TCLK).
(Emulation package 9.6.0.00172)

when either trying the Run | Load option or the Run | Debug option. Using the same project and debug probe with one of our older designs using the same processor works fine so we are satisfied the debug probe and configuration is correct.

  • We have checked the processor clock is correct - clean 25 MHz signal on the processor clock pin.
  • We have run continuity and short checks on the four JTAG connections to the processor and they are correct.
  • The 3v3 power supply is correct and the processor is correctly generating its 1v2 supply rail.
  • The !RST pin is pulled high.
  • The "Verify..." option in the CCS General tab of the project Properties dialog runs successfully to completion.

What else might we check?

  • 0
    TI__Guru**** 191886 points

    HI,

      Do you have the RBIAS pin connect to GND through either a 4.7kohm resistor (if you do not use Ethernet) or a 4.87kohm resistor (if you use Ethernet)?

  • 0 in reply to Charles Tsai
    Intellectual 635 points

    The Ethernet pins are unconnected and there is nothing connected to the RBias pin (pin 59). The documentation (Tiva TM4C1294KCPDT Microcontroller DATA SHEET, DS-TM4C1294KCPDT-15863.2743 Copyright © 2007-2014, SPMS399C) suggests this is correct.

    A somewhat confusing sentence is included in note a to table 26-7 where it says:

    The internal Ethernet PHY should not be enabled when RBIAS is not connected. The ROM boot loader will enable the
    internal Ethernet Phy if no code is present in the flash and a 24-25Mhz crystal is attached to the OSC0/1 pins.

    Confusing because the ROM boot loader doesn't seem to use Ethernet as an option and this possibility implies RBias should always be connected, even though several other entries in the documentation suggest the pin should be unconnected if Ethernet is not used.

    I don't see any mention of a 4.7k (as opposed to 4.87k) resistor being used for RBias in the documentation.

    Can you elaborate on why it is important to connect RBias and why 4.7k should be used in place of 4.87k if Ethernet is not being used?

  • +1 in reply to Peter Jaquiery
    TI__Guru**** 191886 points

    Hi Peter,

      The problem is because of the errata. Please see below. Without the RBIAS connected to ground through a 4.7k resistor, the JTAG may not work. Try adding it and let me know if it resolves the issue. 

  • 0 in reply to Charles Tsai
    Intellectual 635 points

    Thanks Charles. I'm very sure that is the issue. I'm just about to go and tack a resistor onto pin 59, but I need to get caffeine levels balanced first. :-)

    I expect I'll come back shortly and mark this as resolved.

    Cheers,
    Peter