This is the connector configuration fitted as standard to
the Nascom 3.
Nascom 2 and S serial printer connections
Serial printers (and keyboard terminals) are connected to
the Nascom 2 via the PL2 connector. External connection to the
computer should use a 25-way D-type socket, which is connected
to PL2 as follows:
Data received by Nascom
Data transmitted by Nascom
Pin 8 of PL2 should be connected to TP3 on the rear of the board
for use as a ‘handshake’ line.
** The printer handshake at this pin is only at TTL (5 volt)
level. Since many printers use a 12 volt handshake connect the
grey wire from pin 8 to a diode (eg 1N4001), the other end of
which is connected to another diode and a 1K resistor. The other
end of the second diode is connected to pin 7 of the D-type, and
the other end of the resistor is connected to pin 20 of the
D-type. The cathodes of the diodes (usually marked with a bar)
are connected together. This is the connector configuration
fitted as standard on Nascom 3.
* These connections are suitable for the normal printers
operating on RS232 and V24 signal levels, ie +12V and –12V. For
printers using 2OmA current loop the input to the computer
should be connected to PL2 pin 9 instead of 3, and the 20mA
output to PL2 pin 12 instead of 6.
Please refer also to the data sheet ‘Use of printers with
Nascom 2 and 3’ (Application Note AN-006)
Nascom 2 and 3 parallel port connections
The recommended connection between the Nascom 3 parallel PIO
port, PL4, and an external connector is by means of a Scotchflex
cable, using a 25-way ‘D-type’ socket for the external
connection. The D-type should also be of Scotchflex type, the