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Note: In systems with I/O expansion, the power supplies on I/O expansion frames can be
attached via DC cable to the power supply on the previous I/O expansion frame in a daisy-
chain manner, or directly to the main power supply. In this case, the 12V DO control on the
main power supply can control all DO EE relays in the entire RTU that were configured by dip
switch for 12V DO. This enables the user to inhibit all DO EE relays in the entire RTU simply
by removing the plug from the 12V DO control in the main power supply. For more
information, see the I/O Expansion and Expansion Power Supply Module chapters below.
The user program can monitor the relay inhibiting status and act accordingly. Also, when the
module's relays are inhibited, any mismatch between the relay position and the output logical
state is ignored.
Module Configuration
Relay Inhibiting
When the dip switch is set to 12V DO, the position of the 2-pin 12V DO
Control connector on the front panel of the power supply module (see
Power Supply Module chapter above) acts as a safety mechanism. When
the 2-pin TB is unplugged from the 12V DO Control (e.g. for maintenance),
power is not supplied via the motherboard to the relays and the relays are
disabled. The 12V DO affects all relays in the system that are programmed
to work from the 12V DO (the default in the SBO module) and not the 12V
Main.
EE relays that are programmed for 12V DO operation will disconnect when
12V DO power is shut down and cannot be changed in this state.
The state of the Controlled DO LED (CDO) on the bottom of the front panel reflects the 12V
control as follows:
a.
OFF - 12V is not controlled.
b.
ON - 12V is controlled and exists.
c.
Blinking - 12V is controlled and does not exist.
11-4
Digital Output SBO Relay Module
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