Restriction of autorouter?

On 2/15/2010 1:12 PM, James Morrison wrote:

Telemachus wrote on Mon, 15 February 2010 13:04

I'm still pretty new to Eagle. I've made a few PCB's so far, and

they've turned out great, but I hadn't used the autoroute function at

all until

 

now. I need some advice.

 

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

Hello Brian,

 

Of course, you could do your own experiments to determine this--just backup

the files first.

 

But to answer your question, the auto-router doesn't touch anything that

was routed before it starts. So if you hand-route power and critical

traces then it won't touch that stuff.

 

This is generally good but sometimes if you pushed a critical route just a

bit one way or the other you can fit one more trace through but the

auto-router needs to add a via and things get way congested very

quickly. So be careful where you put your critical routes. Your first

pass of the

auto-router may simple to figure out where congestion is going to occur and

then go back to original design (copy of design before auto-router was run)

and adjust critical traces accordingly.

 

Cheers,

 

James.

 

James,

One other thing: what do net classes have to do with the autorouter? Can

these be used to route only certain classes of signals?

Regards,

Brian

On 2/15/2010 1:12 PM, James Morrison wrote:

Telemachus wrote on Mon, 15 February 2010 13:04

I'm still pretty new to Eagle. I've made a few PCB's so far, and

they've turned out great, but I hadn't used the autoroute function at

all until

 

now. I need some advice.

 

I've already routed a particular area of the board since it is a

measurement circuitry area. However, now that I want to route all of

the digital signals, is there a way to restrict the autorouter such

that it

 

does not mess with my already routed measurement circuitry?

 

Hello Brian,

 

Of course, you could do your own experiments to determine this--just backup

the files first.

 

But to answer your question, the auto-router doesn't touch anything that

was routed before it starts. So if you hand-route power and critical

traces then it won't touch that stuff.

 

This is generally good but sometimes if you pushed a critical route just a

bit one way or the other you can fit one more trace through but the

auto-router needs to add a via and things get way congested very

quickly. So be careful where you put your critical routes. Your first

pass of the

auto-router may simple to figure out where congestion is going to occur and

then go back to original design (copy of design before auto-router was run)

and adjust critical traces accordingly.

 

Cheers,

 

James.

 

James,

One other thing: what do net classes have to do with the autorouter? Can

these be used to route only certain classes of signals?

Regards,

Brian