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Z80 Single (Perf)Board Computer

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obiwanjacobi:
Looks nice. Are you going to put all the wires on top (that is what I usually do) or just the plumbing?


--- Quote from: grumpydoc on April 08, 2017, 09:59:56 pm ---Hmmm, just realised I don't have +5V on the right edge of the board for the TTL level serial port and the parallel port connectors. Could be tricky to get it across.

--- End quote ---

There is still space on the top of the connector to put in extra pins... (fill out to the nearest standard number of pins ;-).
Or an extra screw terminal (two) just below the RS232 connector...?

[2c]

grumpydoc:

--- Quote from: obiwanjacobi on April 09, 2017, 08:17:50 am ---Looks nice. Are you going to put all the wires on top (that is what I usually do) or just the plumbing?

--- End quote ---
No, just the power plumbing, then the solder side is clear for the signal runs.


--- Quote ---There is still space on the top of the connector to put in extra pins... (fill out to the nearest standard number of pins ;-).
Or an extra screw terminal (two) just below the RS232 connector...?

[2c]

--- End quote ---
I have it sorted, If I run the ground line that connects to the MAX232 capacitors under the board an extra couple of pads (dotted lines run solder side, in case it wasn't obvious) I will have room to tap of the +5V going to the MAX232 past the end of the right most quad OR gate and then run it along the set of holes parallel to the 0V run.

I'm actually considering trimming back the parallel port connector to 20 pins, I have loads of 20way ribbon cables already made up with IDC headers but no 24-way ones which I will have to buy.

I originally wanted to put in a right angle double row female header but there isn't quite room, that way if I a matching right angle header on any expansion board it would just plug in.

SeanB:
I remember those under dip capacitors, they were designed to fit either into the board before the chip and be soldered with it, or you could insert it into a folded socket before inserting the chip. The socket with a built in decoupler was also common, often as a retrofit, or used on DRAM blocks.  you also got long strips with the power pins on there as pins, soldered into the board top and bottom, and then your chips were arranged on 8 hole spacing all the way down, so you could put all SSI TTL in there on a double sided board, and have only a power and ground feed at the one end of the board while the power strip provided both power and ground, along with distributed decoupling for the chips. You just needed a 100uF 10V electrolytic at the board power input for bulk capacitance. Expensive, but was common on a lot of military stuff as it made design a lot easier if you needed more than 30 SSI packages, and did not want to make an expensive 4 layer board. Was also very common on wire wrapped boards, got rid of a lot of the ground bounce issues there.

grumpydoc:
OK, well I had hoped to have the sockets placed and all the +5V "plumbing" done before the Easter break but, not quite.

Construction is shaping up nicely though



I'm still in two minds whether to get a right angle header with longer pins and flip the CF card 180o so that it sits over the PIA & SIO which would be neater.

The small PCB to the right is a USB serial adapter.

obiwanjacobi:
Looks good!


--- Quote from: grumpydoc on April 12, 2017, 07:17:58 am ---I'm still in two minds whether to get a right angle header with longer pins and filp the CF car 180o so that it sits over the PIA & SIO which would be neater.

--- End quote ---

I would first get it working. The way it is now gives you access to the chips for debugging/probing.
Just try to target each pin with only one wire (on the bottom side I gathered) and it'll be easy enough to replace later on.

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