User`s guide

Connecting GPIO • 38
Version 1.2 July 2010
Input Connections
Current on these inputs must be limited to 20 mA
or less, through the use of a current-limiting resistor. An
external power source (24 volts DC maximum) is rec-
ommended for all inputs and outputs, to prevent ground
loops between equipment.
However, if customer equipment is completely iso-
lated, using power from the GPIO port connectors is
acceptable. Figure B-4 shows details for both types of
connections:
Figure B-4 GPIO input connections