TMS320F2808: JTAG Connectivity

Hi,

I'm designing a board with TMS320F2808 device and look for some assistance on implementing JTAG connectivity. I will use a standard 14-pin JTAG connector with only one single device in the unbuffered JTAG chain. The distance between JTAG connector and target device will be somewhere around 3 inches or so. My problem is that I can't determine the best way to use pull-up and/or series termination resistors on individual JTAG and EMU signal lines. I reviewed schematics of F2808 ControlCARD by TI and EzDSP 2808 emulator by Spectrum Digital and they offer different approach. I've also read an SPRU655I document by TI and it recommends yet another scenario. Namely,

- F2808 ControlCARD uses pull-up resistors on EMU[1,0] lines and pull-down on TRST line only;

- An EzDSP design utilizes pull-ups on EMU[1..0], TMS, TDI, and TCK lines and pull-down on TRST line. This design also uses series termination resistors on TDO and TCKRTN lines;

- An SPRU655I (Figure 10, p22) suggests both series terminations and pull-ups on EMU[1..0] lines. It also suggests series terminations on TCK, TCKRTN, and TDO lines, but provides neither series terminations nor pull-ups for TMS and TDI lines.

Some other designs I've seen use no series terminations at all but utilize 10K pull-ups on all of the JTAG and EMU lines except TRST, which uses pull-down. These designs work but seem to not follow SPRU655I recommendations.


My questions are below.

Q1. It's my take that I should use BOTH 51 Ohm series terminations AND 10K Ohm pull-ups on EMU[1..0], TCK, TMS, TDI, and TDO lines. Is that correct?.

Q2. Should I also use 51 Ohm series resistor for TCKRTN line or could that resistor be ignored and JTAG connector pins (pins 9 and 11) tied directly together due to the very short distance (appr. 0.1 inch) between them?

Q3. It's my take that series resistors for EMU[1..0], and TDO lines should be located near respective pins of the target F2808 device. Is that correct?

Q4. I further assume that series resistors for TCK, TMS, and TDI lines are to be located near respective pins of the JTAG connector. Is that correct?

Q5. If pull-ups are also needed, what about their respective locations?

Please advise.


Regards, Michael