Hello everybody,

I can't get no JTAG connection to SAM9R64-µC on my board. So I found already a design bug: I'm using an external crystal oscillator and because no oscillator bypass is implemented in boot ROM (BMS=1), I wan't be able to use external (serial flash) program code loading. Futhermore, the 32k crystal doesn't run. Changing load capacities (10, 15, 18, 22pF) and crystal type doesn't change nothing.

So here my questions:
- Is it possible to use JTAG-connection with BMS='1' and without external clock (only internal slow clock is valid)?
- Do I need both main- and 32k-oscillators to get JTAG working? Which one is relevant for JTAG interface when executing code from boot ROM?

Thanks for any ideas!

You should be able to SAM-ICE (JTAG) or similar when BMS=0 or 1. I dont like internal RC system clocks so I would advise you use the external slow crystal clock osc. If the uC runs up OK on the slow clock it will switch over to the external fast crystal clock osc. I have been using the SAM9260 and I find that my circuit draws 25mA from 3.3V bench supply at startup then when the fast osc runs up the supply current increases to 92mA, this I take to indicate that the oscillators are both running up OK. My slow crystal (CL=12.5pF) shows as a 200 - 300mV signal when viewed on an oscilloscope.

I have had a lot of problems with PCB's when using small via signal connections required of BGA and large QFP designs. Even if the PCB is bare board tested the assembly can sometimes cause PCB failure. You really need top quality PCB manufacture and assembly techniques and have more than one board assembled to feel anywhere near confident that your circuitry is connected as expected. If you use the external osc at least you can check that its oscillating.

It seems that the SAM-ICE(JTAG) will operate using the internal RC osc provided you have a good external fast osc connected, I used a 12MHz crystal for the fast osc on the SAM9260 but it seems the SAM9RL64 requires 12MHz crystal only and is a requirement for normal operation.

Connection to a comms monitor program using the debug port will allow communication with the internal SAM-BA when BMS=1 (see section 14 of data sheet.

So I did redesign my board and now it works! The problem was: If BMS='1' and no external crystal is connected to main oscillator, no communication via JTAG is possible. It seems to me that's not a feature but a bug... I would expect, that if a MCU has in internal (slow) oscillator than JTAG communication is always possible...