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Knug
Beginner
143 Views

Can I set a weak pull up resistor on an output port ?

Hi,

The PFL we are using has a pull-up resistor 10K on the fpga_nconfig line (output from PFL within CPLD MAXV & input to the FPGA) but currently have issues of the fpga-nconfig line driven low somehow (cannot figure out).

I've seen on the internet comments from people saying the a weak pull up can be set only on input or bidirectional ports. Is this the case ?

Because when I set this manually within the .qsf for the output port fpga_nconfig :

         set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to fpga_nconfig

 

& later looked at the Assignment Editor, noticed that it accepted it as a weak pull up. But it replaced the:

  • 'Assignment Name' from : Location ->  Weak Pull-Up resistor
  • 'Value' from: PIN_E5 -> On

Did not attempt to run this yet.  

Where is eg the PIN_E5 pin location assignment gone for the fpga_nconfig pin? It's been now replaced by a Weak Pull-Up resistor and removed the PIN_E5 location assignment.

Please comment here !

 

Regards,

Kevin 

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6 Replies
Knug
Beginner
127 Views

Replying to myself here. Resolved part of my query..

Ok, within the Assignment editor can also see further down the list the location assignment PIN_E5 for fpga_nconfig.  So I could see that the 2 following location assignments I defined within my .qsf were both listed within the Assignmenr Editor window  

set_location_assignment PIN_E5 -to fpga_nconfig

set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to fpga_nconfig

 

Q/  BUT is is ok to set a WEAK_PULL_UP_RESISTOR on an output port ?

If this is not ok, I must go and set this up from the FPGA side which is declared as an input port.

But it will not resolve the problem I am trying to resolve at the moment ie to why nconfig is pulled low after programming/configuring the loadware PFL code before even autodetecting the flash to program it with the main application code that later on should configure the FPGA

 

Knug
Beginner
120 Views

Can someone please answer my following question before end of the day, so I can attempt to try it out to see if it resolves my problem ?

Q / Is is ok to set a WEAK_PULL_UP_RESISTOR on an output port ?

& can I set a WEAK_PULL_UP_RESISTOR on a port that has already an external pull-up resistor of 10K ? 

Knug
Beginner
95 Views

Tried the weak pull up resistor BUT it did not resolve the issue I had !

 

NurAiman_M_Intel
Employee
78 Views

Hi Kevin,


Thank you for contacting Intel community.


Apologize for the delay in response as I just received this case today.


Per my understanding from MAX V pin connection guidelines, connect this TMS and TDI input pins to a 10-kΩ pull-up resistor to VCCIO1.

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/dp/max-v/pcg-01012.pdf


The Weak Pull-Up Resistor option should not be used at the same time as the Enable Bus-Hold Circuitry option. This option must be assigned to a pin or it is ignored.


Let me know if this is not the answer you are looking for as what I understand is you wanted to know if weal pull up resistor can be set to output port or not.


Regards,

Aiman






NurAiman_M_Intel
Employee
51 Views

We do not receive any response from you to the previous answer that I have provided. This thread will be transitioned to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.


Knug
Beginner
40 Views

I did not finally set a weak pull up resistor on fpga_nconfig.It had already a 10k pull-up.

I resolved the issue I had by myself to why FPGA was NOT configured after successful flash programming

Wrt other tickets raised had to delay the pfl_nreset to get the 1 PFL solution to work.

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