ZiLOG Z80 User Manual page 21

Step 6
Fit and solder connector P3 and P4.
Take care to ensure the pins are parallel to the circuit board.
Connector P3 is optional, so if you want to put the RC2014 in a case or just don't like
the look of it, you can leave this connector off. Alternatively you might prefer a
different connector, such as a female header socket.
Connector P3 pin 15 is a ground terminal between the two port I/O connections.
You may wish to remove this pin before assembly, so that it is easier to visually
identify required connections. Alternatively you may feel an extra ground pin in
more useful. See schematic for pin-out.
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