Electronic – Parallel bus trace width and spacing

designparallelpcbspacingtrace

I have been working on designing a PCB for a Z80 computer that I plan to sell a few times for interested people. The Z80 will work at a maximum of 8 MHz and has parallel lines going to a system controller and an SRAM chip.
The board is 170×110 mm in size. Currently I use 16 mil traces for the parallel bus and address lines and a spacing of 25 mil between them. I wonder whether this is enough for 5V data @ max. 8 MHz. Do I need termination resistors?

What do you think?

Best Answer

I think that's excessively big. I normally use 8 mil width and space unless there is a good reason not to, and I don't see one here.

8 mils is something just about any board house in the world can do, usually with a little extra margin so that nothing is being pushed to the limit. If you know the board house and that they can do finer line/space, then that's fine. Just realize that you may not be able to dump it on any board house, at least not for the lowest price. 6 mil width/space is still well within the capabilities of many processes. At 4 mil width/space you need to know the board house and that they can do it reliably, not just say they can do it.

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