How to report latency at a sink pin in encounter

Hi Sanjay,

Thanks a lot for clarifying. What you're trying to do makes sense to me now. Encounter does support what you're seeking to do. There are a couple of key building blocks you'll need.

First is a "MacroModel". A MacroModel is a mechanism the tool uses to model the insertion delay and load downstream from a sync point in the clock tree. When building CLK2 you'll want to create a MacroModel that describes the insertion delay downstream from the input pin of the instance CLK2 is built from. If CLK2 had an insertion delay of 0.5ns, it would look something like this:

MacroModel pin a/b/c/d/CK 0.5000ns 0.5000ns 0.5000ns 0.5000ns 0.0pf

You can get the tool to generate a MacroModel for you when you're calling ckSynthesis on CLK2 with "ckSynthesis -macromodel . The last field is the load of the pin. I'd recommend making that 0.0pf in your scenario because the input pin cap of the instance you're building CLK2 from has a .lib to model its input pin cap (I presume) and any capacitance you have in this field is additive with what is modeled in a .lib. The reason it may be created as something other than 0.0pf is because MacroModels were originally created to model completed clock trees for partitions, in which case the input pin cap might not be captured in a .lib for the partition depending on the stage of implementation the design is in.

Okay, once you have the MacroModel for CLK2 you're ready to work on CLK1. You can tell CTS to stop on a/b/c/d/CK with the "LeafPin" construct in you clock tree spec file. When you want to specify the clock tree for CLK1 you want to inform it of the presence of the MacroModel file. You can do this by sequential calls to specifyClockTree like this:

specifyClockTree -clkfile CLK2.clockSpec
ckSynthesis -macromodel CLK2.macroModel
cleanupSpecifyClockTree
specifyClockTree -clkfile CLK2.macroModel
specifyClockTree -clkfile CLK1.clockSpec
ckSynthesis

I hope this gives you a good starting point. You can find more information on this in the SoC-E User's Guide in the Clock Tree Synthesis section.

Regards,
Bob

Hi Sanjay,

Thanks a lot for clarifying. What you're trying to do makes sense to me now. Encounter does support what you're seeking to do. There are a couple of key building blocks you'll need.

First is a "MacroModel". A MacroModel is a mechanism the tool uses to model the insertion delay and load downstream from a sync point in the clock tree. When building CLK2 you'll want to create a MacroModel that describes the insertion delay downstream from the input pin of the instance CLK2 is built from. If CLK2 had an insertion delay of 0.5ns, it would look something like this:

MacroModel pin a/b/c/d/CK 0.5000ns 0.5000ns 0.5000ns 0.5000ns 0.0pf

You can get the tool to generate a MacroModel for you when you're calling ckSynthesis on CLK2 with "ckSynthesis -macromodel . The last field is the load of the pin. I'd recommend making that 0.0pf in your scenario because the input pin cap of the instance you're building CLK2 from has a .lib to model its input pin cap (I presume) and any capacitance you have in this field is additive with what is modeled in a .lib. The reason it may be created as something other than 0.0pf is because MacroModels were originally created to model completed clock trees for partitions, in which case the input pin cap might not be captured in a .lib for the partition depending on the stage of implementation the design is in.

Okay, once you have the MacroModel for CLK2 you're ready to work on CLK1. You can tell CTS to stop on a/b/c/d/CK with the "LeafPin" construct in you clock tree spec file. When you want to specify the clock tree for CLK1 you want to inform it of the presence of the MacroModel file. You can do this by sequential calls to specifyClockTree like this:

specifyClockTree -clkfile CLK2.clockSpec
ckSynthesis -macromodel CLK2.macroModel
cleanupSpecifyClockTree
specifyClockTree -clkfile CLK2.macroModel
specifyClockTree -clkfile CLK1.clockSpec
ckSynthesis

I hope this gives you a good starting point. You can find more information on this in the SoC-E User's Guide in the Clock Tree Synthesis section.

Regards,
Bob