Hardware reference guide

I/O Modules
520
35013379 11/2011
External Wiring Recommendation
1. When the green channel status LEDs are off, the module is not generating
outputs, however, an output may still be present if the master override signal is
used.
2. Master override is an input connected via an internal relay contact to the output
when the module is not active. If connected to an external source, the master
override input must be fused by a 1/16 A fuse.
3. If the master override is not connected to an external source, then it must be
connected to common of that channel.The master override relay transition time
is typically 2 ms.
4. The master override inputs must be from an external supply with a source
impedance of <200Ω or tied to system common. These inputs for channels that
are in use should not be allowed to float and may be unique for each.
Diagnostic
During normal operation, the front panel Active and 1 ... 4 green LEDs are ON. If bus
communication to the module stops for any reason, the Active LED will go off and,
depending on panel software configuration:
z when LEDs 1 ... 4 are ON, the channel output levels will be as predetermined and
held by the module.
z when LEDs 1 ... 4 are OFF, the master override levels are output on each
channel.