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

Hi Markus,

> 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.

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

Markus Knauss schrieb:
> 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

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.
...

> 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)? 

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


Markus

Ben Twijnstra wrote:
> Hi Markus,
> 
> 
>>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.
> 
> 
> 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
> 
> 
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

Hi Larry,

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

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

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

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

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

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

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

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

Markus Knauss wrote:
>> Is the flex-cable soldered directly on the pcb of USB Byteblaster?
>> How is this flex cable connected to the USB ByteBlaster?
>>
>> Thanks,
>> Larry
> 
> 
> 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
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
www.amontec.com
------------ And now a word from our sponsor ------------------
Do your users want the best web-email gateway? Don't let your
customers drift off to free webmail services install your own
web gateway!
--  See http://netwinsite.com/sponsor/sponsor_webmail.htm  ----

Hi Ben,

thank you very much for your measurements. I would say that the TCK 
signals on my board look exactly identical.

Although I think that these signals look a bit strange because of the 
drop from 3,3V to 2V. For me it seems that the level converter in the
cable is poorly designed.

I have send the waveforms I have measured to altera. As soon as
I get an answer from them I will also post it here in the newsgroup.

The solution for me at the moment ist using Byteblaster MV instead of 
USB Blaster :-(

It can't check the cable with the Nios - Board because I have only got 
the schematics and not the board.

Best regards

Markus


> 
> Does this look familiar or is it way off?
> 
> Also, if you have an Altera NIOS board lying around, could you try to
> compare the waveforms between your USB Blaster and the diagram attached?
> 
> If they are way off, you may indeed have a problem with the USB Blaster.
> 
> Best regards,
> 
> 
> Ben
> 
> 
> ------------------------------------------------------------------------
> 
> 
> ------------------------------------------------------------------------
>