Electronics > Projects, Designs, and Technical Stuff

How to even start routing this?

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T3sl4co1l:
Yikes! EMI-wise, you're probably slightly better off building this on solderless breadboard with a metal backplane.  It absolutely will ruin your design: I've breadboarded a mere Z80 + RAM + couple bus latches system on one solderless breadboard panel, and had it freeze up at random times due to poor signal quality.  (The randomness was due to implementing an LFSR in the main loop; with the usual loop (an LED display routine), it was fine.)

The resistor placements look like they were determined based on spacial balancing (i.e., a row of this here, a row of that there..), with no regard for where they connect?

Tim

IconicPCB:
I would like to let Topor chew on this and see what it spits out.

If You are Ok with this please send pcb file.

Joanna_H:
I'm seriously considering abandoning the TTL approach, it's fun, it's challenging, but I just went throught the BOM of what I've developed so far and lets just say that it's starting to get pricey....   lots of different boards, lots of B2B connectors, lots and lots of TTL chips.   Adds up quickly.

I'm starting to think I could achieve the same goal using a number of FGPA's (cheaper ones) that would 1) lead to lower cost, 2) require less PCB's and 3) a hell of a lot less routing!

rstofer:
Without a BOM, it's pretty hard to see how much logic is involved with the project.  If most of those chips are MSI, I think the entire project will fit in a small FPGA.  Perhaps we're not seeing the entire project, just one sub-assembly.

A smallish FPGA will have millions of gate equivalents.  Think of an FPGA as a dumpster full of logic with a bunch of RAM on the side.

The bigger problem with the FPGA is getting all the external signals to fall in the range acceptable to the chip.  These days that is usually 3.3V signals.

A separate issue is packaging.  Most of the FPGAs use BGA packaging and I'm not up for that.  But I can buy 'stamp format' boards and just solder them in to a daughter card.

I might consider something like the A7-35T variant if I wanted a 'stamp format' board:
https://store.digilentinc.com/cmod-a7-breadboardable-artix-7-fpga-module/

All the hard work is done, all I have to do is handle the inputs and outputs and write a little code.

mikeselectricstuff:

--- Quote from: rstofer on August 03, 2019, 06:30:04 pm ---A separate issue is packaging.  Most of the FPGAs use BGA packaging and I'm not up for that.  But I can buy 'stamp format' boards and just solder them in to a daughter card.


--- End quote ---
There are plenty of FPGAs in QFP, which isn't a big deal to hand solder

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