define the global routing and detail routing in P&R

define the global routing and detail routing in P&R

Global routing is done to provide instructions to the detailed router about where to route every net. It provides the channels for interconnect to be routed.

Detailed routing is where we specify the exact location of the wires/interconnects in the channels specified by the global routing. Metal Layer information of the interconnects are also specified here.

global routing is the routing with estimated values(delay values based on the fanout of the wire)..this estimated values can be taken according to statics by observing previous manufactured chips....

detailed routing is the routing with actual delays of the wires....this actual delays can be obtained by several optimizations..(Timing optimizations,CTS with good effort(if our design has multiple clocks)) ......................

HOpe u will understand...............Cheers.........

God bless u guys

hi pmaheswara
i am not able to follow your words,,
does that mean that global route and detail route are same sought of algarithm or they do the same functionality but the delay values will be different ,is am with you,,,


but i dont feel that global route and detail route are same sought of algarithms,,,, they are totally different , global route tell the route which channel to acquire and detail route tells in that channnel which track has to be taken...


But i have a doubt here that does the global route also says which metal layer to be used or does this will be decided by the detail route

CAN SOME ONE SHARE THIER VIEWS

According to the tool feasibility and the design feasibility the nanorouter divides the entire portion of the design into switch boxes called as G-cells which consists of tracks which are not actual wires....And the interconnection within the g cell is called as intercell and the interconnection between one gcell to other g cell is called intra gcell........This is the concept of Global Routing...( This is like a plan for Detail Routing)..

Detail Routing is done based on the Plan which the tool has made in Global Routing for those wires which were not actual in global route becomes actual wires now in detail route.....Here wt happens is it does search and repair iterations to make it actual and free from DRC Violations....

Hope this is clear now..If u still have any doubts then u can ask me.....I am here to help u out..

Reply me

what is the difference between channels and tracks?

Hi VLSI
Thanks for the clear explanation, i am happy with your words, You had mentioned about the tool and design feasabilities ,, can u say what are these and they depend on,
Can you tell me how the nanoroute knows about the no of track available in the G-cell, does it is the no of total tracks in all available metal layers, and does also gives a plan for detail route whcih tells which net should go in which layer (may not be the actual track but it will assign the channnle and the layer) am confused about the o/p of global route which passes to the detail route.
HOPE I MADE MY ISSUE CLEAR TO U

Added after 3 minutes:

HI
Channel is the space availble between two obsturcts for routing and track depends on the metal layer width which will be a tech depended

Sorry its manufacturing feasability....

Added after 4 minutes:

manufacturing feasability means when u do fabrication at that time ur metal layers has to be on the grid right ? so this is the thing it will check....and tool feasability is like routing constraints , algorithms and so on.............how many metallayers it has to use...etc

Hope u got this...

Added after 5 minutes:

global route and trial route are one at the same so instead of trial route u can do global route....don't get confused here....
Hope it is clear for u
Bye