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Visitor abfontao
Visitor
5,668 Views
Registered: ‎04-09-2008

cmd_en behavior

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Hi all.

Just in case anyone has happen to be suffering the same problem and knows any solution / suggestion.

When I drive a cmd_en pulse on my mig-based design, I am supposed to be popping an instruction onto the command fifo. In my case, I'm reading from the SDRAM, using a 64-word burst and starting from the address 0. Once this pulse has been issued, the MCB should start to pop data into the reading FIFO... but.... in my case it never does.

I wait for the calib_done signal to be asserted before issuing the cmd_en pulse.

You can see it in the chipscope monitoring image attached.

 

Any idea on why the reading process never starts?

cs_sim.JPG
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Visitor abfontao
Visitor
6,079 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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After testing it: I can confirm what I posted before: the calib_done signal is asserted twice and during the first assertion, any command will be ignored.

 

Is it a design error?

View solution in original post

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9 Replies
Teacher rcingham
Teacher
5,666 Views
Registered: ‎09-09-2010

Re: cmd_en behavior

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What FPGA?
Which version of ISE and MIG?

------------------------------------------
"If it don't work in simulation, it won't work on the board."
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Visitor abfontao
Visitor
5,665 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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FPGA: XC6SLX45T (on a SP605 board).

ISE: 13.2.

MIG: 3.8.

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Instructor
Instructor
5,659 Views
Registered: ‎07-21-2009

Re: cmd_en behavior

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I believe the read latency is roughly 22 cycles.  I'm not sure that your simulation extends long enough.

 

-- 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.
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Visitor abfontao
Visitor
5,657 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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Yes, it does:

cs_sim_2.JPG
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Visitor abfontao
Visitor
5,653 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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Does it make sense that the c3_calib_done signal is asserted twice (erroneously) and during the first assertion all operations send to the MCB are not taken into account or end in failure?

This post seem to support my theory:

http://forums.xilinx.com/t5/MIG-Memory-Interface-Generator/DDR3-on-SP605-spartan-6-Incorrect-calibration-gt-calib-done/m-p/159034

 

I'll test it and post the results here.

Thanks everyone.

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Visitor abfontao
Visitor
6,080 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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After testing it: I can confirm what I posted before: the calib_done signal is asserted twice and during the first assertion, any command will be ignored.

 

Is it a design error?

View solution in original post

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Instructor
Instructor
5,611 Views
Registered: ‎07-21-2009

Re: cmd_en behavior

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This is a good problem to submit for webcase support.  If it's a bug, you'll need to open a webcase anyway.

 

-- 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.
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Visitor abfontao
Visitor
5,600 Views
Registered: ‎04-09-2008

Re: cmd_en behavior

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Webcase submitted. Waiting for the reply. I'll keep you informed if I get a possitive answer.

Visitor gicquiaux515
Visitor
5,594 Views
Registered: ‎04-13-2011

Re: cmd_en behavior

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Hi,

 

ok thanks to keep us informed.

 

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