Implementation

[pennisiag]

Hi all.

I synthesized all blocks of my design using SynplifyPro, version F-2011.09-SP1, creating edif netlist.

After that I created an ISE (ver. 13.4) project importing all edif netlist (top and all other sub-modules).

Target FPGA: Virtex6 xc6vlx760-ff1760-1.

During MAP process I have some warning like this:

WARNING:Pack:2238 - Function generator symbol
   "i_top_Subsystem/i_top_icm/core_hwdata_RNISUJG1_o6[22]" (Output Signal = i_top_Subsystem/i_top_icm/N_483_0_i) has an invalid use of the LUTNM constraint. There are no other function generator symbols with a matching LUTNM constraint value (LUTNM=i_top_Subsystem/i_top_icm/TOP_ICM_lutnm001254). The constraint will be ignored.

I didn't find any documentation about this type of warning.

Please, could someone explain me what's happening?

Thanks in advance.

Regards.

Tino

[bwade]

LUTNM constraints are used to pair LUTs into a single LUT complex. There is no other purpose for the constraint so if only one instance with the LUTNM value is found this warning is printed. What is probably happening is that the other LUT is being trimmed in the early stages of map. You can check your SynplifyPro netlist to confirm that there were two instance at that point. It will be an HLUTNM constraint in the netlist. Then check the trim report (.mrp) to confirm that the missing LUT was trimmed.

[pennisiag]

Hi bwade,

thanks for your response.

You are right. I checked inside SynplifyPro netlist and I found two instance of "TOP_ICM_lutnm001254" with HLUTNM
 contraint. But checking inside MAP report I didn't find any trimmed instance named "TOP_ICM_lutnm001254". There is only the related WARNING:Pack:2238 message.

What it means? Considering that I am using SynplifyPro only for generate edif netlist and I am using ISE to finish FPGA implementation, is it possible that some SynplifyPro synthesis options are used in a wrong way?

I attached run_options.txt of my SynplifyPro project.

Thanks in advance.

Best Regards

Tino

[bwade]

The two instances should have different names but the same HLUTNM value. I think you are confusing the HLUTNM value for the instance name. Besides map trimming another thing to look for is whether you are using the map option -global_opt which is a resyntheis option that may be optimizing one of the LUTs away.

[brucey]

Hi, as you said that there are two instances of same value with HLUTNM constraints, I think this is Synplify issue. HLUTNM can only applied for two instances in the same hierarchy. And you can confirm that these two instances are in different hierarchy. If so, you can ignore these warnings.

[pennisiag]

Hi all. First of all thanks a lot for your response.

Below the portion on edif file under investigation.

          (instance (rename TOP_System_AHB_Master_hwdata_RNII8371_o6_10 "TOP_System_AHB_Master_hwdata_RNII8371_o6[10]") (viewRef PRIM (cellRef LUT3 (libraryRef VIRTEX)))
           (property INIT (string "8'hCA"))
           (property HLUTNM (string "TOP_ICM_lutnm001253"))
          )
          (instance (rename TOP_System_AHB_Master_hwdata_RNII8371_o5_10 "TOP_System_AHB_Master_hwdata_RNII8371_o5[10]") (viewRef PRIM (cellRef LUT3 (libraryRef VIRTEX)))
           (property INIT (string "8'hCA"))
           (property HLUTNM (string "TOP_ICM_lutnm001253"))

So brucey, do you think that it is a SynplifyPro issue?

Moreover I am not using the map option -global_opt into my ISE project.

Best Regards

Tino

[brucey]

Hi,Tino,

From your message, we can't ensure that these two instances are in different hierarhcy.

You can check if these two instances are in different "cell" in you edif file.

If so, it's synplify issue. The warning can be ignored.

If not, we can investigate it further.

[pennisiag]

HI brucey,

I checked inside SynplifyPro edif and I found that the two instances refer to different hierarchic cells, but the functionality is the same: similar inputs going into a multiplexer (implemented in a LUT) with the "same select signal".

So I suspect that "resource_sharing" and/or "enable_prepacking" SynplifyPro project options lead to this type of MAP warning.

What's you opinion?

Thanks in advance.

Regards.

Tino