Connecting To The Auxiliary I/O Interface - Matrox Indio Installation And Hardware Reference

Connecting to the auxiliary I/O interface

The Matrox Indio board has an auxiliary I/O interface composed of 16 optically
isolated auxiliary signals that support sinking and sourcing configurations. 8 are
inputs that receive up to 24 V, and 8 are outputs that support up to 24 V. For
TTL-compatible voltages on output and for sensing at TTL-logic levels on input,
you must adjust your board's jumper settings (discussed later).
Note that sinking and sourcing concepts refer to the conventional current flow,
which means current flows from the positive potential towards the negative
potential. A sinking device provides a path to sink current towards ground or to
the return path; a sinking device does not provide power. A sourcing device
provides a path that sources current; it provides a path from the power source. In
the following diagram, the device on the right is the sourcing device, and the device
on the left is the sinking device.
Sinking
device
Equivalent circuit only
Connecting to the auxiliary I/O interface
Vcc
+
Sourcing
-
+
-
device
23