ANCILLARY DATA |
51
Parallel Port
There are 8 open-collector outputs, and 8 open-collector inputs, each configurable from the Settings menu in the
user interface. The DB25 connector is pinned out as follows:
DB25 Male Connector
Parallel Outputs 1-8
Outputs are open collector to ground, and can sink up to 125mA of current each (actually, any output can sink up
to 400mA, however the maximum combined current should be kept below 1000mA). When an output signal is
active (i.e. “asserted”), the output pin will connect to ground. An equivalent schematic for the outputs is shown
below.
If you wish to interface directly to 5 volt logic inputs, the outputs include a pull up resistor to 5 volts. If you need a
logic high greater than 5 volts, you may supply an external pull up resistor (2.2k
Ω
to 10k
Ω
is appropriate) to the
voltage level required by your external logic inputs. You cannot use a voltage level less than 5V, however you may
use up to 50V.
If used with a relay or LED, then tie your external power source ground to pin 25 (or use the 5VDC power supplied
on pin 1), and run this power source through your device, with a resistor in series to limit maximum current to less
than 125mA.
Equivalent circuit for the parallel outputs
