UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

Reply
Accepted Solution

Spartan6 Suspend-Pin unconnected

Teacher
Posts: 8,355
Registered: ‎07-21-2009

Re: Spartan6 Suspend-Pin unconnected

Here is the initial webcase response:

 

As you mentioned, UG380 states that the SUSPEND pin must be tied LOW for configuration. If this requirement is not respected the memory cell array may not be initialized correctly. Random data in the configuration memory, causes contentions.  It is important to ensure the SUSPEND pin is low during power up and configuration.

  • If the SUSPEND pin is left floating and if the bitgen option is enabled, there is the possibility that the FPGA will enter into SUSPEND mode.
  • If the SUSPEND pin is left floating and if the bitgen option is disabled, I would expect that the FPGA will not enter SUSPEND mode as the SUSPEND pin will be ignored. You should not be able to accidentally enter into a Suspend mode if the pin floats, but you will have other power and noise implications on the pin.  

We have not characterised behaviour other than SUSPEND being tied LOW for power-on and configuration, as this is our recommendation, and so, we cannot guarantee the behaviour if SUSPEND = 1 at power-on.  Therefore, it is difficult to predict what will happen.

-- Bob Elkind

SIGNATURE:
README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

Summary:
1. Read the manual or user guide. Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts. If I write a good post, then I have been good for nothing.
Visitor
Posts: 6
Registered: ‎04-19-2012

Re: Spartan6 Suspend-Pin unconnected

I have patched my 6-layer-board (mill the board from rear side till the ball of FPGA) and connect the suspend-pin to GND. But the FPGA don't configure.

 

So I have inspected everything over again and have found my mistake. One mode-pin was not connected properly!

Thanks all for help!

patch.png
Teacher
Posts: 8,355
Registered: ‎07-21-2009

Re: Spartan6 Suspend-Pin unconnected

Congratulations on finding the error.

 

Nice photograph!

 

-- Bob Elkind

SIGNATURE:
README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369

Summary:
1. Read the manual or user guide. Have you read the manual? Can you find the manual?
2. Search the forums (and search the web) for similar topics.
3. Do not post the same question on multiple forums.
4. Do not post a new topic or question on someone else's thread, start a new thread!
5. Students: Copying code is not the same as learning to design.
6 "It does not work" is not a question which can be answered. Provide useful details (with webpage, datasheet links, please).
7. You are not charged extra fees for comments in your code.
8. I am not paid for forum posts. If I write a good post, then I have been good for nothing.
Teacher
Posts: 2,113
Registered: ‎09-09-2010

Re: Spartan6 Suspend-Pin unconnected

I suggest that you glue all modification wires to the PCB to reduce the risk of them becoming detatched.

------------------------------------------
"If it don't work in simulation, it won't work on the board."
Instructor
Posts: 9,048
Registered: ‎08-14-2007

Re: Spartan6 Suspend-Pin unconnected

Just a note for next time you need to debug this sort of problem:

 

Impact allows you to view the state of the configuration pins.  You should have been

able to see the state of the mode pins as seen by the internal logic just by using

one of the debug functions of Impact.  Especially with BGA's this is a valuable tool.

 

When I design a board with BGA's I typically require the layout designer to place a

via for each unconnected pad just in case I find I needed to make a connection.

It helps you to avoid the sort of rework you show in your nice picture.

 

-- Gabor

-- Gabor