Help me to set clock metal layer preference!

[praneshcn]

Clock Routing

hi,
on wat basis and which layer do we set clock metal layer preference in a 8 metal layer design.



thnx

 

[vamsi_addagada]

Clock Routing

hi based on u r choose u want 3or 4 or 5 metal layer u r using for clock rounting.and u maintance the double width and double space of the clock routing

vamsi krishna

 

[praneshcn]

Re: Clock Routing

yes vamsi ur correct for a 8 metal layer design we can prefer metal 4 &5. but on wat basis? why do need metal 4 & 5 to be selected. y cant 6 do the job. Explanation needed.


thanks

 

[ypnayak]

Re: Clock Routing

wese genreally 4-5 layer

 

[vlsitechnology]

Clock Routing

because if we use higher layers then our resistance decreases but at the same time the capacitance increases so wt we generally do is we prefer M4 and M5 for clock routing.......................

If a design is a 16 metallayer then u use M8 and M9 to balance both R and C values...........
Hope u got it

Bye take care

 

[chipmakers]

Re: Clock Routing

Hi

S.. As vlsitechnology said , If we use higher layers then our resistance decreases.. So that Current Flow Wil be Increases....
Its not like, In 8 Metal Layer Design,We Prefer 4 & 5 for Clk Routing... Mine is 8 Metal Layer Design... We chose M8 for Clk Routing,Since , In M8 , Resistance wil be Less Compare to M4 M5... So that It wil useful to Achieve the Timing....

Regards...

 

[vlsitechnology]

Clock Routing

Yes ur right in that way also we can think but when we are talkng about the IR drop we need to use lesser resistance metal layers
that is if u got more ir drop then wt we do we try to divide the current by adding more and more stripes but if the metal layer is lower then our i mean if we are taking M2 and M3 in a 6 metal layer design then it becomes a problem
and it will cause EM problems and timing problems and so on
so in order to achieve an effctive design we have to compensate all these things
correct me if i am wrong?

take care

 

[xinsu]

Clock Routing

for layers,you'd better chose 2 continuios layers,for route priority,you'd better route ahead of other signals.

 

[chipmakers]

Re: Clock Routing

Well... Mine is 8Metal Layer Design... Used M8 for Clk Routin, M6 & M7 for Power Structure...
Gettin Lesser IR drop Value....
As u said, M7 & M8 Using for Power Structure, M6 will be using for Clk Routing, Does it help in Meeting the Timing?

Regards

 

[vlsitechnology]

Clock Routing

Yeah according to my knowledge it will meet timing

 

[sandeep_torgal]

Re: Clock Routing

In a 8 level metal system, always use the top level metals for power routing. Try to floorplan in such a way as to meet the timing for clock routings. The best is to use somewhat 4 or 5 and the spacing as mentioned earlier to be double to reduce the coupling cap.
ALso avoid using lower metals as they will be densely used and probably coupling and resistance will be more.

Hope this answers the query.

Regards,
Sandeep

 

[praneshcn]

Re: Clock Routing

Hi,

In magma where do we specify the tool to use double spacing for clock routing. Hw 2 do tat?


thnkz

 

[chipmakers]

Re: Clock Routing

Magma "rule nondefault" Will help u...
Used to Creates a nondefault routing rule for a library...

Try this..

 

[rohini_p]

Re: Clock Routing

hai praneshcn

since you want it for clk nets try it out when you perform CTS.
fix clock command has the nondefault option.

wbr
rohini