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Observer s1gandhi
Observer
287 Views
Registered: ‎06-24-2019

disable out of context synthesis in top down flow

Hi

I am creating a top down flow, width various IPs which have been configured with OOC enabled, with their own xdc files.

For the top level synthesis, i want to disable all the xdcs, any out of context synthesis or dcp generation and have only the top level xdc to be applied.

Can someone explain me the steps / commands which i need to apply to generate a synthesized netlist ? What i see now, is its generation various DCPs, eventhough i have not marked them as OOC in the top level project .

Thanks

Sameer

 

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3 Replies
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Historian
Historian
216 Views
Registered: ‎01-23-2009

Re: disable out of context synthesis in top down flow

When you create an out-of-context (OOC) .dcp (synthesized or even implemented) the .dcp contains the constraints that were used to synthesize/implement the design.

However, as you are aware some of these constraints are required only when the design is synthesized/implemented OOC - namely constraints on ports of the OOC module that are supposed to connect to the "upper" level of the design (these would be things like create_clock, set_input_delay, set_output_delay) and constraints that would be used when the module is used, regardless of whether it is OOC or now integrated into a top level design  (internal exceptions, create_clock/set_input_delay/set_output_delay on ports that connect directly to top level pins of the design).

There is already a mechanism for controlling this, using the -out_of_context flag for the read_xdc command. If you do

read_xdc <filename>

Then this xdc file is used both when the design is synthesized/implemented OOC and when it is integrated into a top level design (i.e. these constraints are "imported" to the top level design when the .dcp is read in).

If you do

read_xdc -mode out_of_context <filename>

Then this xdc is only used for the OOC synthesis/implementation - these constraints will not be used when the design is read in as part of a top level design.

(I think this is what you are looking for...)

Avrum

 

Observer s1gandhi
Observer
108 Views
Registered: ‎06-24-2019

Re: disable out of context synthesis in top down flow

Thanks

But still need some more clarification.

If someone has already created an IP, is it possible to mark that file as "ooc" ? or i need to remove the file probem that IP project, and add it back using tcl command ?

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Observer s1gandhi
Observer
104 Views
Registered: ‎06-24-2019

Re: disable out of context synthesis in top down flow

also, i believe, you mean, while i create a block or IP, i should read the file with mode set to out of context. This automatically ensures, that when i integrate this IP in the top level, this constraint is not applied when i set the IP mode to Global . Please confirm.

thanks

 

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