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CC3200MOD JTAG PIN MUX USAGE

Sandeep Yayathi
Prodigy 50 points
Other Parts Discussed in Thread: CC3200MOD, CC3200

Hello,

I'm having trouble getting a handle on the MUX usage of the JTAG pins. In the two boot modes that use JTAG (Functional 2WJ and 4WJ).
These pins are required for JTAG usage. However the DS and configurator allow you to configure these as I/O pins.

If these pins are used as I/O in the design and they get configured as soon as your application boots, How would you ever use the JTAG functionality.

In addition if you were to be running the application with a DEbugger hooked up and the same lines were used to control devices on your board by the code. 
Even if there were no other issues with reusing the pins...I have to imagine it would be impossible to run the debugger in an application that required the use of those pins as I/O

The more I look at this the more I feel like its not really possible to use the JTAG as I/O. Am I missing something about the procedure here....is there some time window during boot where the application code can be prevented from running and JTAG is available?

In the case where you need the JTAG lines would you have to put the chip in UART Load mode and try to execute the application using a JTAG interface ?

Getting close to the end of a design that must be completed in the next day or two! If you can call me that would be great.

  • 0
    Guru 39650 points
    Hi,

    In real live can be used pins 16 a 17 for application purpose in case of using SWD instead of JTAG for debug. Pins 19 and 20 is better to reserve for debugging. SWD works with IAR and latest CCS (6.1.3).


    Jan
  • 0 in reply to Hnz
    Prodigy 50 points
    So if I'm hearing you right,

    1. I should be able to access SWD over the FTDI if I'm replicating the launchpad interface design??
    2. I should reserve the JTAG_TCK / JTAG_TMS for software debug (This is pin 21 and pin 22 on the cc3200MOD)
    3. I could still reuse the JTAG_TDI (pin 12 ) and JTAG_TDO (pin 18) as GPIO with no issues since the only purpose of the JTAG interface in this device is for debug
    4. Device programming is done in UART mode so I will be able to program the device still regardless of the above choices.

    Is that accurate?

    Thanks for your input on this!
  • 0 in reply to Sandeep Yayathi
    Guru 39650 points

    Hi,

    CC3200 scan SOP pins after reset. According this PINs its select bootloader mode (SOP2) or JTAG/SWD (SOP0). Using SWD allows to save two pins (TDI/TDO) and still allows use debug in your real device. But if you don't need this two extra pins (GPIO22 and GPIO23) use standard 4 wire JTAG. You will not have any problem. In previous versions Code Composer Studio (6.1.2 and earlier) was bug with SWD debug. Actually SWD debug was not functional. This bug was reported by many users of e2e forum, TI employees was not able reproduce this issue.

    1. No. You not need change reference design. Launchpad design allows to use SWD. Only you need set differently SOP0 pin.

    2. Yes. I think is better to have available debug capability at final hardware. But if you not need debug in your final product, you can also use this two PINs for your application.

    3. If you switch CC3200 to SWD by SOP0 pin and in PINMUX change TDI/TDO PINs to GPIO you get extra two IO pins and you will have still capability to debug by SWD (TCK/TMS). But if you not need this extra pins, consider to use 4 wire JTAG.

    4. Yes. First (factory) programming sFlash need to be done by UART. Programming at customer side is better to do by OTA update.

    Jan

  • 0 in reply to Hnz
    Prodigy 50 points

    If you are using TMS and TCK for software Debug in this case. Should you leave them "Unassigned" in the PIN MUX Utility?

    Or must you configure them some how?

    Thanks

  • 0 in reply to Sandeep Yayathi
    Guru 80445 points
    Hi,

    Yes, you not need set this pins. Pins TDI/TDO/TCK/TMS are configured for JTAG/SWD as default - please see table 3.1 in SWAS032F. Mode JTAG/SWD is set by SOP pins.

    Jan