Points Reachable/Unreachable in Conformal LEC

[englishdogg]

So it was a true unreachable - great

 

[amitk3553]

Re: lec unreachable

Here is the Scenario of the Problem I am facing.
1.Read a Golden Design and a Revised Design

Map the Points and Compare

2.Read the Same Golden Design and The Different Revised Design.

This time the Revised Design has been created by changing some Constarints in DC


The Problem I am facing is
Some Points in the Golden Design are not reachable for the First Run , But they are NOT_MAPPED for the Second Run

How this can be? because Conformal Says NOT_MAPPED unmapped points are reachable but do not have correspoding point in the Logic Fanin Cone of the Corresponding Design.

So How the same Point in Golden which is reachable becomes unreachable when the revised is changed....


Thank You,
Sachin Shahsikantrao Pampattiwar

1)Unreachable points never affect your functionality.Means e.g. if you are finding some FF unreachable,then its fully sure that the FF in not affecting your functionality.so check that point in Golden and check the functionality

2)use set mapping method -keep_unreach

3)See the affect by changing synthesis variables(Related to minimizing the area) also in global_dc_variables file

 

[englishdogg]

you contradict your points 1 and 2
In (1) you mention that they never affect your functionality then in (2) you mention to use -keep_unreach option..
Pls suggest why. to my knowledge and experience these lead to false non-eqs in the design.

 

[amitk3553]

you contradict your points 1 and 2
In (1) you mention that they never affect your functionality then in (2) you mention to use -keep_unreach option..
Pls suggest why. to my knowledge and experience these lead to false non-eqs in the design.

By using it some not mapped points which are due to unreachability are also mapped.
if –unreach is not in the mapping method, and during
verification (where some Not-mapped points may be ‘promoted’ to Extra
due to unreachability.)

Although Unreachable does not affect functionality, but just some unmapped due to unreachability are also mapped using keep_unreach.Design looks FULLY GREEN.Otherwise no need to use.