Program Older Fpga Board With Jtag 3

[Alex]

Here is a question a customer about programming JTAG 3 with older FPGA board. Can someone help on this? 

 

Questions

I was wondering if I could use the JTAG 3 cable to program older digilent fpga boards that use the 6 pin connector?

I understand that the connector is different, but if I hook up the right signals from the 14-pin connector to the right pins in the older 6-pin header, that should work as well right?

 

 

[JColvin]

Hi Jordi,

 

That's alright, we all make mistakes sometimes. I am by no means an FPGA expert, so I'll need sbobrowicz to confirm my answer but here is my understanding:

 

After checking out the reference manual for the JTAG-HS3, I believe the reason that this is a pure 14 pin cable is so that the Zynq-7000 chip on ZYBO boards is able to be programmed correctly since that pin (pin 14) needs to be connected to pin 14 of the JTAG header and driven low at the appropriate times. Because the header is a 2x7, the 1x6 connector naturally cannot connect to all 7 pins simultaneously so the board is programmed correctly.

 

That being said, if you are programming a different board that only requires the 6 pins, I would think that in theory you could individually route the signals from the HS3 to the 6-pin MTE connector with wires, although I don't know how this would affect the programming since it's hard to guarentee the wires are the same impedance so that signals pass through at the correct times and whatnot.

 

The main issue, at least from my point of view, is that the pins on the HS3 and a 6-pin compatible cable (like the JTAG-HS1) are not in the same physical location, so you would not be able to plug in the 6-pin MTE connector straight into the HS3 and have it work correctly. Again, you maybe could route the wires individually, but that might result in some iffy programming; I have never personally tried this. 

 

Either way, the 14-pin connector is recommend simply because it brings all the signals of the HS3 to the correct pins on the FPGA without any issue or user re-routing.

 

Let me know if you have any more questions. (and correct me if this is not accurate sbobrowicz)

 

Thanks,

JColvin

[sbobrowicz]

The JTAG3 cable actually has a 6-pin connector on it and can be used to program Digilent boards with a 6-pin jtag header. No conversion to or from a 14 pin connector will be necessary

[Jordi]

If that's the case, I don't understand the following statement on digilent's site: 

 

"* This is a unique programming header and is not compatible with the 1x6 MTE Digilent JTAG Connector." 

 

 

http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,395,1298&Prod=JTAG-HS3

 

 

 

 

Thanks.

[JColvin]

Hi Jordi,

 

I believe that particular statement is for the Xilinx 2x7 connector which is for the JTAG-HS3. What they are referring to is the JTAG3, which actually a different product, although I agree that it is a confusingly similar name; it took me awhile to notice the difference. You can see it at the bottom of the programming solutions product page here: http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,395&Cat=5#JTAG3

 

Let me know if you have any more questions.

 

Thanks,

JColvin

[Jordi]

Hi JColvin,

 

thanks for your answer, but actually, my original question (posted by Alex) was about the JTAG-HS3 and not about JTAG 3. Sorry about that. I've just noticed the mistake...

 

I gather from your answer that the JTAG-HS3 cable would not work with the older digilent boards with the 6-pin connector? Even if I hook the right signals from the 14-pin connector to  the 6-pin MTE connector?

 

 

Thanks!

[Alex]

Hi Jordi & everyone, I am sorry for the typo. Yes, the original question is related to JTAG HS3 instead of JTAG 3.