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Explorer
Explorer
5,329 Views
Registered: ‎12-21-2009

Constraint Ignored

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Hi all,

 

I'm using the PlanAhead 13.3 to debug on the FPGA. I generate the NGC netlists for my design using my XST scripts then import them all to PlanAhead13.3. I have the following in the UCF file:

 

INST "/gen_sil_clk/PLL_ADV_INST" BANDWIDTH = OPTIMIZED;
INST "/gen_sil_clk/PLL_ADV_INST" CLKIN1_PERIOD = 10.000;
INST "/gen_sil_clk/PLL_ADV_INST" CLKIN2_PERIOD = 10.000;
INST "/gen_sil_clk/PLL_ADV_INST" CLKOUT0_DIVIDE = 10;
INST "/gen_sil_clk/PLL_ADV_INST" CLKOUT0_PHASE = 0.000;
INST "/gen_sil_clk/PLL_ADV_INST" CLKOUT0_DUTY_CYCLE = 0.500;
INST "/gen_sil_clk/PLL_ADV_INST" COMPENSATION = SYSTEM_SYNCHRONOUS;
INST "/gen_sil_clk/PLL_ADV_INST" DIVCLK_DIVIDE = 1;
INST "/gen_sil_clk/PLL_ADV_INST" CLKFBOUT_MULT = 4;
INST "/gen_sil_clk/PLL_ADV_INST" CLKFBOUT_PHASE = 0.0;
INST "/gen_sil_clk/PLL_ADV_INST" REF_JITTER = 0.005000;

 

When i perform ngdbuild using command line these constraints in the UCF file are accepted without warnings

Contrarily when the planAhead performs ngdbuild it gives me warning about the above constrains like this:

CRITICAL WARNING: [Constraints 18-11] Could not find cell '/gen_sil_clk/PLL_ADV_INST'

 

So, the constraint is accepted by the ngdbuild when running in terminal mode but the planAhead ignores them saying that it cound not find the Cell !!!!

 

Any suggestions ?

 

Thanks in advance.

 

 

 

 

 

 

 

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1 Solution

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Xilinx Employee
Xilinx Employee
6,569 Views
Registered: ‎07-01-2008

Re: Constraint Ignored

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Is that leading slash correct? I don't normally see that. Check the .bld file to see what the PA run is doing differently.

View solution in original post

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5 Replies
Xilinx Employee
Xilinx Employee
6,570 Views
Registered: ‎07-01-2008

Re: Constraint Ignored

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Is that leading slash correct? I don't normally see that. Check the .bld file to see what the PA run is doing differently.

View solution in original post

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Explorer
Explorer
5,315 Views
Registered: ‎12-21-2009

Re: Constraint Ignored

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I separated the constraint for the PLL in a separate file and loaded the two UCF files in the project so, the critical warnings desappeared.



Regarding you suggestion:

The slash is working fine with ngdbuild when used in command line mode. There is no error with the slash, I'm using it with other instants in the UCF and all those constraints pass without ignore.

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Explorer
Explorer
5,303 Views
Registered: ‎12-21-2009

Re: Constraint Ignored

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I removed the leading slash as you suggested and the constraint was successfully parsed by PlanAhead. But it's strange that the ngdbuild in command line mode did successfully parse the constraint.

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Guide avrumw
Guide
5,297 Views
Registered: ‎01-23-2009

Re: Constraint Ignored

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But it's strange that the ngdbuild in command line mode did successfully parse the constraint.

 

This is not entirely unique. There are cases where "legal" UCF constraints are not handled by the planAhead parser. The two parsers are quite different. The parser in ngdbuild has been around for a LONG time, and has had a lot of fixes implemented over the years. The net result is that it can parse a lot of syntax; some of it odd, and some of it archaic.

 

The parser in planAhead is relatively new (only a couple of years), and can definitely "miss" things.

 

One important thing to realize, though, is that if planAhead cannot understand a constraint, and issues a critical warning, it will NOT pass that constraint to ngdbuild; planAhead does not just pass your .ucf files directly to the ise tools, but instead, writes out its own .ucf file for the implementation process - you can see it under the impl_1 directory. When there is a critical warning, the offending constraint will not be in this rebuilt ucf file.

 

Avrum

Explorer
Explorer
5,291 Views
Registered: ‎12-21-2009

Re: Constraint Ignored

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The ignored constraints were really critical that they caused the bit file generated using my scripts functional on the FPGA while the bit file generated from planAhead with some debugging nodes has shown some data signals as rubbish and the HW returned wrong results.

 

I used the planAhead constraint editor. I find it really nice and helpful. It helped me generate the correct constraint. I recommend it over the ISE constraint editor.

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