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I normally don't autoroute anything, but I'd like to try it on a board I'm working on. Problem is this board is 8 layers and my seat is limited to 6 layers. I'm thinking I can remove the layers where I have the power and gnd planes from the stack up and disable those nets in CM. Then add the layers back in after the routing has been done.
If this will work, how do I "lock" any existing traces I have routed to prevent the autorouter from moving them?
I don't use autorouter either, but I think placing the "fixed" property on the clines will lock these lines.
I feel like I could never get autorouter to do anything I wanted it to do. :) Good luck.
In reply to Mstrghettorigg:
MstrghettoriggI feel like I could never get autorouter to do anything I wanted it to do.
I feel like I could never get autorouter to do anything I wanted it to do.
My sentiments exactly.
There is one area on this board that I want to see if it can save me some time. I have most of the critical stuff in so I figured I'd give it a shot at the rest of the signals. We'll see..........
You have your planes marked as PLANES in the stackup? Specctra doesn't count power planes against the 6 layer count.
In reply to redwire:
Tom the specctra Autorouter is pretty darn good as autorouters go, but the real power with specctra is in its ability to manualy route a board. The interface is a whole lot different than Allegro as it is an old hold out from the Days of CCT. Things like the silkscreen do not appear in specctra only etch/pins and vias, copper objects, keepouts etc.
I can tell you without reserve that if you have access to Specctra with your current license and you take the time to give it a whirl you will find you can blow through routing boards. The route editor as it is called in specctra is amazing easy and natural to use. There is also really good intergration with Allegro in that you can launch it from Allegro etc. The big advantage is that allegro can pass the design rules to specctra so you wont have to bit fiddle setting things up.
Be aware ! that specctra uses files with the ".dsn" extension "Same as capture" Love that : )
When you start specctra, It can be started in a few ways. One of them invokes full autorouting but by default from Allegro it should just invoke the program and sit there until you hit the go button in specctra.
In specctra you use the function "Protect Wires" to disable them from getting auto-routed.
To do this and there are a couple of ways, go to the tool bar and choose "Select > Wires "Sel Wire Mode" or select all to select all wires. Next go to Edit Menu and choose " UN Protect " wires by net. "'Protect and UN Protect" are compined into the same menu ! , You can also protect Vias.
By way of another tip. Click on the "Edit Route Icon" Then RMB "Setup" Good defaults are
Snap to Pin Orign, Push Routing "Turn off to just hug routes", Allow Redundant wiring on enabled nets and Multiple Pins Connections"
One More thing. When you launch Specctra at the bottom Right corner of the screen is a button that is used to show the current units you are using. Make sure this is set correctly. MM for mili meters, mil, inch etc for imperial units. Check this as your first step.
Others might dis-agree here but for routing a board manually Specctra cant be beat..
Enjoy : )
In reply to ScottCad:
This sounds very interesting. I did not realize that manual routing could be done there also. Since I knew it as an autorouter I stayed away from it. I will try what you suggest this evening and see how it works.
In reply to TH Designs:
I agree 110% with Scott. I used Specctra to manual route almost all the boards I did when I was using Mentor Boardstation. There are still some things that it can do that even Allegro still can't do. For example: one thing EE's liked is that you can go into Shadow mode and bring up the netlist and cycle through each net in the design and auto fit each selection. Just use the down arrow key in the list and you can easily go through a 500-1000 net design in a day. I am sure other old CCT users can site more. Still a great stand alone tool.
Tom I tell you, when you see what the specctra route editor can do you will be a convert.
I would like for you to try this.
Click edit route mode, use your middle scroll wheel on your mouse to kind of draw a box to zoom in to some pins, now simply with your left mouse depressed draw a little box around say 4 pins that have nets attached.. You will see all the nets can be routed in one go, thats cool eh. Now while those nets are getting routed in right click and select "Gather Bus wires" and if your license allows it you will see some very neat stuff : )
Everything in specctra is so easy when you get the mechanics down. Things like selecting nets, pins, changing vias, wire width etc will more than likely have you asking yourself why bother doing it in Allegro : )
Here is a little pointer.. Say you are routing 4 traces in.. use the center mouse button or wheel button to pan as you route along.
Hope you have fun with it.. as boma pointed out it is a awesome tool.
Tom BTW you can also use Specctra to move Placed Parts or even place a packaged design prior to routing.
In reply to Boma:
Right on Boma : )
Specctra has been around forever the cool part about it is, Your actual PCB editor might be good at place and edit but as long as you have specctra you can be sure no matter how crappy that pcb editor is you can still manually route a board ha ha
I tried using the autorouter and couldn't seem to get the hang of it. Are there any "Specctra for Dummies" type of docs I can read? I know I didn't allow myself enough time with it as I had a tight deadline to meet this weekend so I went with manual routing using Editor.
Tom I had not seen any tutorial's on Specctra, Perhaps I should make a YouTube video that goes over the basics :)
I have used it for a long time and it can take awhile to get used to it but it is fairly easy. When you are in Allegro you can invoke specctra from the Allegro Tool-Bar. "Route > PCB Router > Route Editor" This will start Specctra and allow you to manualy route a board.
Traces that have been routed in Allegro may appear with a white-line through them in Specctra. This means these routes are protected so you would have to un-protect the routes in specctra before you could re-route them or edit them.
The keys so to speak in spectra for certain actions are done by selections so in the case of protected traces we could "select all wires first then un-protect all of those selected nets and finally un-select all routing objects so they are no longer selected.
Sounds a bit difficult in e-mail, if you were to see it done you would think it is fairly simple and kind of makes sense.
The other thing about specctra is pretty much all PCB editors can export their PCB in the specctra format for routing of a board. This means that you could support routing boards from a wide variety of PCB tools with your cadence tools and thats kind of cool.
Here is a blow by blow to do list to get you going.
Configure your Grids First " View Display Grids" There are grids for wires,vias,placement. leave the box that says factor set to -1
Configure Your Layer Colors "View Layers" Color palette at the bottom of the layer screen. When your colors are set go back to the layer screen. You will notice the actual layers in your design. Click on the color box beside a layer name to turn the layer on and off. Also notice there is a pop down box to choose routing bias on a layer as you change things you will notice the command window will tell you what you did.
Next select View Guides All to turn on the rats nest if it is not on
Last click the edit route icon to route manually. Click on some pins with nets to route those suckers in. Use RMB for additional options.
Thats about it.
When you did your training course did they not cover Specctra ? in the class.
I have been having issues replying to posts. I log in, hit reply and I get kicked out. Guess they are getting tired of my inane questions / comments.............. Hopefully this post goes through.
Thank you for your tutorial on the autorouter. I have not yet tried any of the latest suggestions, but hope to over the weekend.
The training course I had was a three day course and just covered the basics. It was an emmense help as I would probably still be floundering without having taken it. I'd have to take the advanced course to get into autorouting. Since I do 99.9% manual routing, I don't think an advanced course is in my future.
Hi Tom, I had difficulty logging in too. Might have been an issue with the server.
On the autorouter, I dont autoroute any boards, never have like you all my routing is done manually. I just use specctra to do this as I have found it to be more productive than using the manual routing tools in allegro.
If you ever want to dig into that part of the allegro suite "Specctra" a little deeper and have some spare time, drop me a note, be glad to assist if I can.
i dont use autorouter either
from my experience, using autoroter, disregards the following(or i may have wrong settings):
2. differential routing
3. limiting the use of vias
and with regards to your question, autorouter seems not to change previously routed traces, instead, it routes to avoid these existing traces.
In reply to jemarods:
1,2,3 These are license based features. Pretty much you need GXL. It will honor these.
As far as it avoiding previously routed traces -- it depends. If you did not tell Specctra it could reroute them it won't. It's worth digging in to the user manual and checking out the Specctra overview slides Cadence has.