• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 82 subscribers
  • Views 548 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.

TMS320F28027F: f28027f

Ahsan
Intellectual 625 points
Part Number: TMS320F28027F

Hi,

My question is related to JTAG circuitry on PCB. First I copied the schematic mentioned on page 25 of tmsf2802x datasheet. According to suggestion, additionaly I had to add DIP switch for TRST, TDO and GPIO34 with pull up and pull down resistors as shown in picture below

1) Normally for the normal operation of MCU, the TRST' should be at high or low state?

2) The TRST' will be connected to 3,3 volts when switch is on. Is that safe to use?

3) As it can be seen from Launchpad f28027f, there are Tx and Rx pins for communication but in the devices manuals, I have not seen these pins for communication with JTAG. Which type of communication will be done with xds110?

4) The GPIO34, TDO and nTRST are connected to JTAG header and their respective pins of MCU with pull down resistor of 2.2k. Is that fine diagram for JTAG?

Thank You

  • 0
    TI__Guru* 80200 points

    Ahsan,

    For the nTRST the PD is sufficient, there is no need to have an option to tie high.  The emulator/debug probe will pull this high when it is connected, and is the only reason nTRST should be driven high.

    For TDO/GPIO34 you can look at page 2 of the LAUNCHXL-F28027 schematic you'll want to put option with the switch for either PU or PD for boot reasons.  JTAG will overdrive TDO when connected as long as you use a relatively weak pull.

    For Q3, if you are implementing the XDS100v2 or XDS110 on your PCB locally, you can connect SCI pins from the F28027 through this port if you want for comms across the USB to the PC host.  This is NOT needed for debug/CCS connection, but taking advantage of spare logic on the FTDI device that is acting as the XDS100v2 or the TI device that is action as the XDS110

    Q4) yes this value is fine, as is the 820 used as PU when in series with the 2.2kOhm.

    Best,
    Matthew

  • 0 in reply to MatthewPate
    Intellectual 625 points

    Hi Matthew,

    Thank You for your detailed answer.

    In point 2 you have mentioned about about weal pull in case JTAG is overdriven. I haven't got this statement as I am using pull down of 2.2k for nTRST, TDO and GPIO34. This is exactly the schemetic of launchpad f28027f. The pull up resistor for TDI and GPIO34 is 820 ohm. While the netlist TDI and nTRST are connected to JTAG header which can be seen from below mentioned diagram. Finally I have modified connections and are these connections are fine to go as I have to order PCB ASAP? The JTAG female header of xds110 will be having polarity or connection marked on it that which pin has to be connected at which side?

  • 0 in reply to Ahsan
    TI__Guru* 80200 points

    This implementation looks good, thank for including the PD on TDO/GPIO34 in your attachment.  Pin 6 is a key pin on the JTAG header, and will have a block in it.  On your board you will need to manually clip off the header pin on pin 6 which will ensure the correct polarity/position for the remaining pins.  

    Best,
    Matthew

  • 0 in reply to MatthewPate
    Intellectual 625 points

    Matthew

    What the menaing of the term 'block on pin 6'? Means there will be identification part from TI on 14 pin header of pin 6. In our case pin 6 is normally connected to ground.

    Regards,

  • 0 in reply to Ahsan
    TI__Guru* 80200 points

    Ahsan,

    I mean that on an emulator that you buy, like XDS200 or XDS110, pin 6 will have a physical plug so that if it is not oriented the correct way it will not plug into the pin header.  In this sense pin 6 is actually a no connect for the JTAG, but for your PCB you can just cut off the pin, it is OK that the through hole for this pin is connected to ground.

    https://e2e.ti.com/support/sensors/f/1023/t/632599?AWR1642-how-to-connect-a-10-Pin-or-14-Pin-JTAG-

    Best,

    Matthew

    www.google.com/url