Hi Igor and Laurent, Thanks for responding. I realised too late that -develop isn't the proper list for this sort of questions.
On Thu, Nov 04, 2010 at 02:12:55PM +0100, Igor Skochinsky wrote: > You don't have to rely on TRST, you should be able to reset the TAP by > sending five clocks with TMS high. Yes, but not on this chip, TMS320VC5501PGF, it needs TRST high to get into the right mood/mode. > If you meant to say that you can't enter debug mode without TRST, > that's indeed the case for XScale chips (and maybe some others). TI tic54x / tic55x too (like the one above). > If you have an MCU board with some GPIOs or can control them from PC, > you can try my JTAG search program to confirm the pin layout. > http://mbed.org/users/igorsk/programs/JTAG_Search/5z843/docs/main_8cpp_source.html > It's written for mbed but should be easy to port to anything with some GPIOs. What an interesting idea! That is a very useful program to help out if you don't know the system's JTAG connectors. It might be a very nice combo with the generic flash access I'm trying, although I cannot connect the dots just yet. > That said, a pull-down resistor should not prevent you from using the > pin. You just need to provide some voltage to override it. I feel a bit hesitant to drive 0,27A into TRST :) but you are basically correct, of course. On Thu, Nov 04, 2010 at 02:25:02PM +0100, Laurent Gauch wrote: > > Do you mean TRST is tied on your target board to GND via 12 Ohm pull-down ? Yes, indeed. > Using a pull-down to TRST is practiced to make sure the TAP go-and-stay > in reset state at the powerup of your target. > TI add pull-down on TRST on all their boards. Yes, their chips then operate normally and are not influenced by the EMU0 and EMU1 signals that might put the device in High-Z. > But a 12 Ohm is a bit too smaller to strong ! > Are you sure it is not 1K2 Ohm ? Quite sure. > If you have a Amontec JTAGkey or JTAGkey-2 you may drives TRST as > push-pull or open-drain. My Turtelizer2 is also open-drain, so it'll pull down from a pullup resistor (that's what I had soldered on it for a previous PCB with the same DSP chip). Thanks, -Rick _______________________________________________ Openocd-development mailing list [email protected] https://lists.berlios.de/mailman/listinfo/openocd-development
