AM335X: Procedure for gaining access to boundary scan

Hi,

What JTAG emulator are you using?

Hi Biser,

  I am using Digilent HS2 programming cable, with some JTAG driver software to emulate boundary scan tester.  It was fine working "directly" with Xilinx boundary scan cells.  I assume I just need to send out preamble bit streams before it can talk to AM335X boundary scan TAP controller.

Thanks, Mark

Perhaps this can help: http://e2e.ti.com/support/arm/sitara_arm/f/791/t/226576.aspx

I tried grounding both EMU0 and EMU1 (as opposed to original pull up to 3.3v), boundary scan tester still can't detect TDO signal from AM3358. Like AnBer suggested, timing diagram should be most helpful.

I'm sorry, but I can't find any additional information on this.

Thank you.  I appreciate your help.

- EMU0,1 can be high, no problem

- TRSTN should be driven by the JTAG controller. Pulling TRSTN low disables the JTAG port

- Main oscillator must be running

- CPU must be out of RESET

- All VDD supplies must be applied to have access to the IO scan cells. (Even for IOs that nobody uses).

regards

Wolfgang

BeagleBone Black connects TRSTn to GND via 4.7K resistor, and thus keep TRSTn normally low.

My JTAG controller don't have TRSTn pin, so I connect BeagleBone Black TRSTn line directly to 3.3V VDD.

After powering up BeagleBone Black, I saw keep-alive LEDs flashing

I run my JTAG test controller few times, The TDO pin still get all 1's, even though I drive some user LED pins (gpmc_5 - gpmc_8, V15, ... V16) to 0.