More thoughts on building a Z-80 (64bit!!!)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Sat Oct 24 23:17:03 1998

< It's a right pain to do complex digital circuitry like this. Great for
< RF amplifiers, etc, but not so easy to run data buses across the board.
< Although you _can_ make striplines using strips of copperclad stuck down
< to the groundplane if you have to.

for bussed logic is can work. The trick I used was 2sided clad board
with one side sliced to produce 8 narrow strips as a bus with it's own
groundplane. It was elevated over the chips with some screws (also passed
the ground) and then wires picked off the needed signals. this approach
was used to hook a 8049 MCU to a DDS (digital synth) that was used to
drive a PLL. The core of a DDS is a (this case) 24bit parallel adder and
24 bit accumulator plus a 24bit constant register. A lot of parallel
bussed signals. It was all clocked at 16.777216(2^24)mhz.

A ram card would be harder but I've done one (dram!) that was fairly
small (1Mx8 using 256kx1 dips) and one off. busing is a pain only in
that it's a lot of repetitive wiring. But being visible it was easy to
see signal progression. The results worked well and lacked the ringing
that sometimes plagues boards of two sided design.

Allison
Received on Sat Oct 24 1998 - 23:17:03 BST

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