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Buffers of the same direction cannot be placed in series.
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04-27-2012 09:04 AM
ERROR:NgdBuild:770 - IBUFG 'ddr3_inter_inst/u200_iodelay_ctrl/se_clk_ref.u_ib
I used clock wizard to generate a 200M clock to support DDR3 MIG clk200_ref, it synthesize successfully, but when I translate the design, it produce this Error message, how can I solve this problem? (by the way, ISE v12.1)
Re: Buffers of the same direction cannot be placed in series.
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04-27-2012 11:48 AM
Both MIG and clock gen wizard have been told (or assume) an external (package pin) source for the clock. Both core generators are inferring input buffers. When you connect MIG and clock gen signal ports together, then XST sees cascaded (series) input buffers.
In the MIG-generated source code, follow the input clock port signal through the wrapper code to the infrastructure.v code, and edit the infrastructure.v file to remove the redundant buffer.
You are clearly using either Virtex-5 or Virtex-6 device. In such posts as yours, the identity of the target device family is essential information. For core generators such as MIG, output is very different for each device family.
... it synthesize successfully, but when I translate the design, it produce this Error message...
Please explain, what is the difference between 'synthesize' and 'translate' in your post? I consider 'translate' to be part of the 'synthesis' process, rather than two different processes.
Is there a reason you are not using ISE 12.4 or 13.4 instead of 12.1?
-- Bob Elkind
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.
Re: Buffers of the same direction cannot be placed in series.
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04-27-2012 12:28 PM
Hi Bob,
It seems likely that the OP meant by Synthesize the processes that are run under Synthesize, eg. HDLCompiler and XST, and by Translate, he meant the processes run under Translate, aka ngdbuild. The main output from the Synthesize step is a bunch of ngc files, and the ngdbuild translates those to a single ngd file.
I've found that the translate step (which also evaluates the contraints files) catches various errors in which something was synthesized which is not allowed in the part, either by policy or lack of physical elements or connections.
The particular error in this case seems to be exactly of that type, and was posted by ngdbuild.
Bill
Synth vs. Translate
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04-27-2012 12:37 PM
Thanks, Bill, your explanation makes sense.
-- Bob Elkind
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.
Re: Buffers of the same direction cannot be placed in series.
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04-27-2012 04:01 PM
Thank you for your reply! your suggestion work.











