DC topographical - Cadence Encounter

[vcnvcc]

Hello..

I am using Cadence Encounter, Now I would like to run DC topo.

What file do I have to use to run DC topo. Can you please describe, how do I proceed? Thanks.

 

[ro9ty]

Could you please reply to your question, now that it has been over 8 years?
We would like to know

Ro9ty

 

[pdude]

ro9ty i guess you got confused. Jis join date is 2006 but the question was asked recently.
Could you please answer it now.

 

[sharath666]

DC topo requires a DEF file apart from the RTL. So the flow is like 1)Run Dc and get a netlist 2)Use the netlist to get a DEF file 3)Run DC topo using RTL and DEF to get a better netlist and use only this netlist further.

 

[pdude]

DC topo requires a DEF file apart from the RTL. So the flow is like 1)Run Dc and get a netlist 2)Use the netlist to get a DEF file 3)Run DC topo using RTL and DEF to get a better netlist and use only this netlist further.

Thanks Sharath but i think there are a lot of other differences because if which we use topo. Since you have used can u elaborate a little.

 

[ro9ty]

Sharath is correct but there are many different ways in which a DC-topo is used.
The work of DC topo is to allow the tool to optimize better based on other inputs like physical constraints, physical only cells etc... that we usually do not provide to DC in normal mode.
For physical constraints we usually supply the DEF to DC topo or it can also accept the MW database. You can separately manually specify the physical constraints also (like die size etc..) and also placement bounds, keepout margins. The main objective is to allow the tool to undertand the virtual floorplan so that it can use it effectively while optimizing.
.
The optimization engine is more robust and accurate. While DC uses the command compile to optimize, DC topo uses compile_ultra. You can man the command and learn more about it.
.
However, DC topo is not always used with the DEF or the placement constraints. It can simpley be used like DC but with parasitics information like TLU+ and SPEF so that the tool is able to do a better optimization based on net capacitances because as the technology is progressing optimizing at every level based on real life parasitic values is becoming essential.

Ro9ty

 

[sharath666]

The main motivation behind developing Dc topo is that we are seeing wide differences between post synthesis results and post P&R results. So EDA companies are trying to incorporate more intelligence into synthesis tools so that it can read physical information also and come out with more accurate results. Synopsys has taken this concept further with DC Ultra. So there is no difference as such between DC and Dc topo. DC topo is more accurate.That's it.

 

[ro9ty]

DC topo has lots of additional features which gets modified with every subsequent release which are not available in DC and hence there is quite a lot of difference. However, yes the endpoint is same- DC topo is more accurate but what makes it so makes the topo features different.

Ro9ty

 

[pdude]

Sharath is correct but there are many different ways in which a DC-topo is used.
The work of DC topo is to allow the tool to optimize better based on other inputs like physical constraints, physical only cells etc... that we usually do not provide to DC in normal mode.
For physical constraints we usually supply the DEF to DC topo or it can also accept the MW database. You can separately manually specify the physical constraints also (like die size etc..) and also placement bounds, keepout margins. The main objective is to allow the tool to undertand the virtual floorplan so that it can use it effectively while optimizing.
.
The optimization engine is more robust and accurate. While DC uses the command compile to optimize, DC topo uses compile_ultra. You can man the command and learn more about it.
.
However, DC topo is not always used with the DEF or the placement constraints. It can simpley be used like DC but with parasitics information like TLU+ and SPEF so that the tool is able to do a better optimization based on net capacitances because as the technology is progressing optimizing at every level based on real life parasitic values is becoming essential.

Ro9ty

Sorry, little out of topic but what is difference between TLU+ and SPEF. Please explain with snippet if possible.