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Altera_Forum
Honored Contributor I
791 Views

Max10 Jtag pins as Differential I/O.

Good day.  

I've got a problem with jtag pin sharing. My device is Max10 10M08. I use jtag pin sharing option and jtag pins as differential inputs. But when I try to program device with sof file using USB blaster, it fail. When this pins are outputs(not diff), programming is OK. When they are inputs (not diff) it fail too.  

 

The JTAGEN pin is pulled-up with 10 kOm resistor to 3.3 V. 

 

So the question is, how to program device using jtag and then use TDO, TMS, TDI and TCK pins as differential inputs?
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4 Replies
Altera_Forum
Honored Contributor I
19 Views

Hi, 

 

JTAG pins cannot perform as JTAG pins in user mode if you assign any of the JTAG pins as a differential I/O pin. 

You must use the JTAG pins as dedicated pins and not as a user I/O pins during JTAG programming. 

 

--- Quote Start ---  

The JTAGEN pin is pulled-up with 10 kOm resistor to 3.3 V. 

--- Quote End ---  

 

Means JTAG pin is used as a dedicated pin. 

Refer https://www.altera.com/en_us/pdfs/literature/hb/max-10/ug_m10_gpio.pdf  

 

Best Regards, 

Anand Raj Shankar 

(This message was posted on behalf of Intel Corporation)
Altera_Forum
Honored Contributor I
19 Views

Thank you for your answer.  

I think that if use jtag pin sharing and pulling-up jtagen, you can program fpga via jtag, and after programming pull-down jtagen and use Jtag pins as diff io (after making them diff in pin planner). As I understand it works only with single ended io. But how can I use jtag pins as diff io? In pin planner I see that Jtag pins can be differential.
Altera_Forum
Honored Contributor I
19 Views

Hi AMKozha, 

 

--- Quote Start ---  

I think that if use jtag pin sharing and pulling-up jtagen, you can program fpga via jtag 

--- Quote End ---  

 

Yes, You have said the configuration for Dedicated JTAG pins. 

 

--- Quote Start ---  

after programming pull-down jtagen and use Jtag pins as diff io (after making them diff in pin planner) 

--- Quote End ---  

 

Not possible. 

If you intend to switch back and forth between user I/O pins and JTAG pin functions using the JTAGEN pin, all jtag pins must be assigned as single-ended i/o pins or 

voltage-referenced I/O pins. Schmitt trigger input is the recommended input buffer. 

 

Let me know if this has helped resolve the issue you are facing or if you need any further assistance. 

 

Best Regards, 

Anand Raj Shankar 

(This message was posted on behalf of Intel Corporation)
Altera_Forum
Honored Contributor I
19 Views

 

--- Quote Start ---  

 

 

Let me know if this has helped resolve the issue you are facing or if you need any further assistance. 

 

Best Regards, 

Anand Raj Shankar 

(This message was posted on behalf of Intel Corporation) 

--- Quote End ---  

 

 

Thanks for your explanation. It's help me to understand why it doesn't work. But my question about using jtag pins as diff io has no answer. Is it possible somehow? 

 

May be using of internal configuration with pof file or two configuration images?
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