Electronics > Projects, Designs, and Technical Stuff
How to even start routing this?
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mikeselectricstuff:
And as there is RAM, bear in mind that you can swap around any address and data pins to help layout.
 
Joanna_H:

--- Quote from: mikeselectricstuff on August 02, 2019, 03:03:00 pm ---Placement
Placement
Placement
Gate and pin-swapping for multi-gate packages, swapping gates between packages where possible.

Do you really need to keep it to two layers ?
How many of these are you making? - unless it's thousands then your time getting to 2 layers is probably worth mor than the additonal cost of 4 layers , bearing in mind that it can probably be smaller on a 4L PCB as well.

--- End quote ---

I'm just having fun with a little project, doesn't have to be 2 layers, etc..   I'm just trying to keep costs down as it'll probably take a few revisions to debug it all.  It's also why I restricted each module size to 100x100mm, to keep costs down.   Yeah, I could have made it a lot cheaper by using a FPGA but that defeats the point of trying to create it out of 74 series.. :D

It's really just a mini (well not so mini any more) project.
Joanna_H:
It's all part of a bigger modular project as described earlier, so it's just lots of 100x100mm boards connected together.   Been going through doing each part and then reliased a graphical output would be nice.  So put that thing together, probably will get changed again, but not sure.  Other stuff has been done, but again needs to be manually routed, it's mostly auto atm just to get an idea of what is going on.

KE5FX:

--- Quote from: Ice-Tea on August 02, 2019, 09:41:06 am ---
--- Quote from: KE5FX on August 02, 2019, 09:07:56 am ---Don't bother with a power plane.

--- End quote ---

But... Why?? Do you hate power integrity? Do you appreciate high frequency noise? What? This will easily fit on 4-layers with GND and PWR planes.. Why not do it 'right'?

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Power for components in this class that are mounted on boards of that size comes from capacitors, not planes.  She's got plenty of bypassing, but not enough routing area.

One nice thing about power planes, however, is that they can be used to maintain copper symmetry.  The board will less prone to warpage if large planes are balanced from top to bottom.   If the power plane is omitted, it's good to maintain a lot of ground islands for that reason.  Don't remove copper unnecessarily, in other words.... but don't ascribe any magical electrical properties to it, either. 
jmelson:

--- Quote from: Joanna_H on August 02, 2019, 06:42:10 am ---Forgot to say, it's a two layer board.

--- End quote ---
2 LAYERS?  The power and ground nets, if made with even slightly thicker traces, will fill almost the entire area, leaving no space for signal routing.  I really don't think you can do it.
If this is all digital stuff, why not use an FPGA?  You might be able to do it in one chip.

Jon
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