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JTAG communication Problems in Quartus using Signal Tap

Hi newsgroup,

I have got problems using Signal Tap with the Altera USB Blaster download cable. Sometimes the data collected is correct, sometimes not, sometimes I get a jtag communication error.

When I use the Altera Byteblaster MV download cable, I don't get those incorrect data nor jtag communication errors in Signal Tap and everything works fine.

In Quartus timing analyzer there are no failed paths.

As suggested in a newsgroup, I have set all unused pins to "inputs tristated".

I use Quartus 4.2 SP1 on windows 2000 SP4. PC ist a 2,4GHz Fujitsu Siemens Amilo D. I tried a different USB cable and a different USB port.

The target hardware is our own board with a EP1C12F256C8, VCCIO is 3,3V. TMS and TDI have a 10k Pullup to VCCIO, TCK has a 10k pulldown to gnd. The jtag connector is less than 2 inches away from the cyclone and this part of the schematic is from the altera nios board.

It seems linke the problem has something todo with the faster timing on jtag when using the USB Blaster. Is it possible to adjust the jtag frequency?

When I look at the JTAG signal "TCK" with the scope, I have the following results:

1.: Using Byteblaster MV: The signal edges reach 3,3V and are looking good.

2.: using USB Blaster: The signal edges reach 3,3V but they break down to about 2,5V. It looks like a sawtooth.

I hope someone can help me in this newsgroup. It would be nice if someone could look at the TCK signal with the scope on his USB Blaster running Signal Tap.

I didn't get an answer from altera mysupport within 1 week.

Best regards Markus

Reply to
Markus Knauss
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Hi Markus,

Do you have a Revision A USB Blaster (with standard ribbon cable to the PCB) or a Revision B USB Blaster (with flex-pcb cable)?

The Rev A cables have signal integrity problems, so in that case, contact your disti for a replacement if you such a cable. This should cost less than a new cable.

Before Dec 1st, 2004 Altera would have swapped your cable for shipping cost, but now the offer has expired, unfortunately.

Best regards,

Ben Twijnstra

Reply to
Ben Twijnstra

Markus Knauss schrieb:

Hi Markus, I use 1k pullup ,pulldown. I had some problems with 10k pulldown on TCK. The following is from "ALTERA Support Find Answers":

.. Problem

Are there any known errors in the Stratix and Cyclone Configuration chapters with reference to the external pull-down resistor value recommended for the JTAG TCK signal?

Solution

Yes. The JTAG TCK pull-down resistor value is incorrectly specified as 10k-ohms in the Stratix and Cyclone Configuration chapters. The correct external pull-down resistor value is 1k-ohm. This stronger resistor ensures that the TCK signal is biased at a logic low level despite the weak internal pull-up on this pin. The internal pull-up ranges from 20k-ohms to 40k-ohms across process, voltage and temperature.

Future versions of the Stratix and Cyclone Handbooks will be updated accordingly. ...

Reply to
Thomas Fischer

I have got a brand new Revision B USB Blaster with flex cable.

Markus

Reply to
Markus Knauss

Hi Ben,

What is the difference between their original ribbon cable and their flex cable.

Is the flex-cable soldered directly on the pcb of USB Byteblaster? How is this flex cable connected to the USB ByteBlaster?

Thanks, Larry

Reply to
Laurent Gauch

Hi Larry,

Apparently, the original ribbon cable was unreliable when used at high speeds in noisy environments. Especially Signaltap was vulnerable to this.

Sorry, I understand your curiosity, but I'm not going to void the warranty on my cable to find out. My guess is that they use stubs to solder the cable to the PCB, but I could be completely off.

Best regards,

Ben

Reply to
Ben Twijnstra

Hi Thomas,

thank you for the hint.

Today I have tried 1k pulldown on TCK. The result was even worse. The TCK signal breaks down to 2V. I get the jtag comm errors earlier.

Maybe my USB Blaster has a defect.

With the Byteblaster MV it works also with 1k on TCK.

Regards

Markus

Reply to
Markus Knauss

Hi Larry,

I opend the case (there is just one screw and no warranty seal).

The flex cable is connected to the usb blaster PCB with a 10 pole connector (2 x 5 poles, 2,54mm pitch).

Regards

Markus

Reply to
Markus Knauss

Thank you for taking time opening the case. Very interesting, since we are building our own USB2.0 JTAG Emulator.

We have to find the best connection for the best signal integrity.

Larry

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Reply to
Amontec, Larry

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