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Subject: Bus to bus wire spacing in Allegro
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pcb_hevi
Posts: 0
Online: User is Offline
12/11/2006 3:37 AM  
I want to create a bus to bus wire spacing rule in Allegro.
I have a board with several busses on it and I want to have a distance between the wires of one bus to the wires of all the other busses of twice the normal spacing. 
How can I define this in Allegro? 
rajpcb
Posts: 16
Online: User is Offline
12/11/2006 7:29 PM  
you can define three Net Spacing rules say BUS1, BUS2 and BUS3.Map this in the assign ment table as below,

BUS1 BUS1  BUS1
BUS2 BUS2 BUS2
BUS1 BUS2 BUS12 or see the picture file attached.

this worked for me. Get back me if you have any issues.

Cheers and Good Luck!!!
Raj.





rajpcb
Posts: 16
Online: User is Offline
12/11/2006 7:31 PM  
Oops... its not BUS3 its BUS12 I used...
pcb_hevi
Posts: 0
Online: User is Offline
12/12/2006 6:51 AM  
Thanks Raj, but I have 32 Busses on my board, so I think this is not the way I can handle it.
Is there any other possibility to handle the bus to bus space in a convenient way?
rb
Posts: 53
Online: User is Offline
12/12/2006 8:11 AM  
Here are some other considerations/alternatives:

How many different spacing rules do you need? I'm guessing that you probably don't need a different spacing constraint set for each bus. If you don't need a different spacig rule for each bus, you can probably get by with only a few different Net Spacing constraint sets. The spacing assignment table would be set up as shown below

bus1 bus1 no_type 5mils
bus1 bus2 no_type 10mils
bus1 no_type no_type 10mils
bus2 bus2 no type 5mils
bus2 no_type no_type 10mils
bus3 bus1 no_type 10mils
bus3 bus2 no_type 10mils
bus3 bus3 no_type 5mils
bus3 no_type no_type 10mils

Also, if some of the buses are physically isolated from each other on the board and/or are assigned to different layers for routing , these buses could probably be grouped together into one net spacing property like bus_10_15. In the following example buses 10 thru 15 would never get near each other because they are either physically in different areas of teh board, or they are being forced to route on different routing layers from each othe with a net physical rule. The assignment table would look like:

bus_10_15 no_type no_type 10mil
bus_10_15 bus_10_15 no_type 5mil


Randy
sandhya.im
Posts: 3
Online: User is Offline
1/31/2008 8:52 PM  
Hello,

I have 5 different buses in my board. Net spacing within each bus is 12 mils and spacing inbetween different buses is 16mils.How can i set these values in Allegro15.7.
Could anyone clarify me.

Thank u
sandhya
shiva
Posts: 57
Online: User is Offline
1/31/2008 11:33 PM  

The settings are same as above give by Raj and Randy. Try it. And get back if you have any difficult.

Regards,
Shiva...
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Forums > Silicon-package-board > PCB Design > Bus to bus wire spacing in Allegro


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