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Re: Help With New WDC65C265 PCB (in EASY EDA) - 1st Time!
Posted: Thu Apr 21, 2022 3:09 pm
by drogon
You are kidding... Not that I have anything against 4-layer boards, but I can't see any reason for 4 layers with classic microprocessors and even contemporary microcontrollers. 2 layers are more than enough if you don't use BGA packages. I do PCB designs for like 25 years, using Eagle and now KiCAD (once it became usable with 6.x version) and have yet to see the necessity of 4-layers. Ok, I don't do anything above 120 MHz; with high frequencies 4 layers would be useful, but few times I did 2 MHz 24-bit ADCs with analog front end and digital back end in 2 layers and it worked better than the earlier 4-layer implementations of the circuits made by some professionals.
These, for example, were done with 2 layers:
https://hackaday.io/project/163755-sdc68k
https://hackaday.io/project/163757-sdc85
That's what I keep saying - my Ruby runs at 16Mhz (both 65C02 with 64KB RAM, and 65C816 with 512KB RAM) on a double sided board designed with Fritzing... There are actually 2 separate 16Mhz clocks on the boards (One for the ATmega) and an SD card being clocked at 8MHz too.
However it is fairly minimal and doesn't run a CPU bus off-board and uses 2 GALs for "glue", but even so... I keep telling myself that I don't have the tools to tell me why it should not work ... and it's been rock solid for years now.
-Gordon
Re: Help With New WDC65C265 PCB (in EASY EDA) - 1st Time!
Posted: Thu Apr 21, 2022 3:36 pm
by BigEd
It's clear, I think, that 4 layers is not essential... but I think the thing to focus on here is that it's not much more expensive, reduces risk of some kinds of difficult to debug problem, and makes routing easier.
So, if you're very cost-conscious, or home-etching, or very confident, or re-doing an existing design, then choosing 2 layers is a reasonable choice.
(It's just possible that there are more ways to go wrong with 4 layers, and produce a completely incorrect design, and that would depend a bit on your tools.)
Re: Help With New WDC65C265 PCB (in EASY EDA) - 1st Time!
Posted: Thu Apr 21, 2022 5:39 pm
by Jmstein7
It's clear, I think, that 4 layers is not essential... but I think the thing to focus on here is that it's not much more expensive, reduces risk of some kinds of difficult to debug problem, and makes routing easier.
So, if you're very cost-conscious, or home-etching, or very confident, or re-doing an existing design, then choosing 2 layers is a reasonable choice.
(It's just possible that there are more ways to go wrong with 4 layers, and produce a completely incorrect design, and that would depend a bit on your tools.)
I just can't seem to do this in two layers.
Re: Help With New WDC65C265 PCB (in EASY EDA) - 1st Time!
Posted: Sat Apr 23, 2022 7:46 pm
by Jmstein7
Okay, I finally finished my first attempt. I tried to follow all your advice the best I could.
Jon
Re: Help With New WDC65C265 PCB (in EASY EDA) - 1st Time!
Posted: Wed May 18, 2022 6:46 pm
by Sheep64
If it's KiCAD, well, I'm trying to learn that too but I haven't actually made any designs in it yet.
Jmstein7: Send me a napkin sketch or KiCAD schematic and I'll return a two layer layout. It'll probably take me more than two weeks to return any design. However, I'm considering a W65C265 or eZ80 design which runs a neutral bytecode. It would be good practice to first work on your design.