• State Resolved
  • Locked Locked
  • Replies 11 replies
  • Subscribers 98 subscribers
  • Views 2668 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Question on JTAG return clock connection

Anonymous
Anonymous

Hi All,

 

I would like to ask a question JTAG connection.

 

 

 

 

In EVM6437, the JTAG return clock signal TCKRET is

1.      First connect to mux/demux U539

2.      Then connect to the output of OR gate U37

But not connected to DSP.

 

So in this way it is not used? Then why still connect or even provide it? Why connect it to the output of an OR gate?

 

 

 

 

Thanks,

Zheng

  • 0
    TI__Mastermind 41665 points

    Zheng Zhao said:
    So in this way it is not used? Then why still connect or even provide it? Why connect it to the output of an OR gate?

    TCK is an output from the JTAG connector, a reference clock provided by the JTAG emulator that feeds into the device being emulated (the DSP), it is not actually clocking any logic in the emulator, in theory you could ignore it and provide your own TCK (not that this would be recommended).

    TCKRET is an input to the JTAG connector, it is the return clock signal that actually drives the emulator's logic, it does not have to actually come from the device being emulated, but it has to be skew matched to what the DSP sees on its TCK input.

    The wiki article at http://processors.wiki.ti.com/index.php/XDS_Target_Connection_Guide may help explain this in a bit more detail. Basically the reason this is being done is so that the TCK_RET signal is skew matched to the TCK signal seen by the DSP, the OR gate is being used as a buffer.

  • Anonymous
    0 Anonymous in reply to Bernie Thompson TI

    Dear Bernie,

     

    I need some time to read this and would reply later.

     

     

    Zheng

  • Anonymous
    0 Anonymous in reply to Bernie Thompson TI

    Dear Bernie,

    I got it, thanks very much.

    Zheng

  • Anonymous
    0 Anonymous in reply to Bernie Thompson TI

    Dear Bernie,

     

    When I am debugging on my EVM board which is from a TI distributor rather than Spectrum, I often got the message “clock skew detected”. Is it a software issue, or hardware issue? Is it possible that this is due to unequal length of wiring of the board (which part could cause this?)?

     

     

     

    Zheng

  • 0 in reply to Anonymous
    TI__Mastermind 41665 points

    Zheng Zhao said:
    When I am debugging on my EVM board which is from a TI distributor rather than Spectrum, I often got the message “clock skew detected”. Is it a software issue, or hardware issue? Is it possible that this is due to unequal length of wiring of the board (which part could cause this?)?

    I have not come across such an error myself, do you get this when you are actually debugging or is this a message that comes up during the build process?

    I ask because searching the E2E forums it seems like this sort of message comes up when the time stamping gets messed up on your files during a build for some reason, in which case it is a software issue during the build that you can usually bypass by trying the build again.

  • Anonymous
    0 Anonymous in reply to Bernie Thompson TI

    Always in build, never in actual debugging.

    I just thought of the connection because of the message "clock skew". It seems not likely a software issue.

     

    Zheng

  • Anonymous
    0 Anonymous in reply to Anonymous

    Dear Bernie,

     

    I have just made new board. For its TCK_RETURN clock, I followed SEED (a Beijing-based TI distributor) schematic example and simply connected TCK_RETURN and TCK together without an intervening buffer.

     

     

    And when testing with the board, I got

    CCS 3.3 error said:

     

    Error connecting to the target:
    Error 0x80002240/-233
    Fatal Error during: Initialization, OCS, Control,
    This error was generated by TI's USCIF driver.
     
    SC_ERR_PATH_BROKEN <-233>
    The JTAG IR and DR scan-paths cannot circulate bits, they may be broken.
    An attempt to scan the JTAG scan-path has failed.
    The target's JTAG scan-path appears to be broken
    with a stuck-at-ones or stuck-at-zero fault.
      
    Board Name: DM6437 XDS560 Emulator
    Cpu Name: ICEPICK_C_0
    Abort:               Close Code Composer Studio.
    Retry:               Try to connect to the target again.
    Cancel:                        Remain disconnected from the target
    Diagnostic:       Run diagnostic utility.

     

    Which I posted as a question in  0x80002240/-233 SC_ERR_PATH_BROKEN Connection error, along with other descriptions. Could you have a look at the post?

     

     

    Thanks,

    Zheng

  • 0 in reply to Anonymous
    TI__Expert 5475 points

    Hi,

    TCK and TCK_RETURN should NEVER be connected together. Just connect this pins directly to the JTAG connector pins.

    Best regards, Zegeye 

     

  • Anonymous
    0 Anonymous in reply to Zegeye Alemu

    Dear Zegeye,

     

    What happens if they are connected together?

    Zegeye Alemu said:

    Just connect this pins directly to the JTAG connector pins.

    What do you mean by this?

    My understanding is that

    1. TCK be connected to DSP's TCK pin
    2. but for TCKRET I have no idea. Should I follow SpectrumDigital EVM6437 schematic example above?

     

     

    Sincerely,

    Zheng

  • 0 in reply to Anonymous
    TI__Expert 5475 points

    Hi,

    It is there. Probably with another pin name like RTCK. If you can't find it let me know and I will look into this. Without these signals you can't debug the device. So, it is there.

    Best regards, Zegeye

  • Anonymous
    0 Anonymous in reply to Zegeye Alemu

    Dear Zegeye,

     

    From spdu079a, page 10, JTAG/MPSD Emulation Technical Reference (http://focus.tij.co.jp/jp/general/docs/lit/getliterature.tsp?literatureNumber=spdu079a&fileType=pdf), it is said that TCKRET CAN be an unbuffered version of TCK.

     

     

    So which is correct?

     

     

     

    Zheng