Rockwell Automation MDO32BNS 32-Channel Digital Output Module - Manual (Page 8)

8 MDO32BNS October 2005 – Issue 7
Triguard SC300E
Figure 2-3. Field output connectors J2 and J3 pinouts
THEORY OF OPERATION
In accordance with TMR practice, channel output command information from the system
follows three identical paths through the Digital Output Module (Figure 2-4) each path at the
command of its own microcontroller in the Common Interface. As the switching speed of the
module exceeds the system scan rate the channel data can be converted to serial form before
entering the module from the Common Interface. In this manner 32 output channels can be
served by just three paths instead of 96.
The three data streams are each applied to opto-isolators which mark the interface between
the system and output sides of the circuit and provide a system to field channel isolation of
1000V minimum.
The data streams are then applied to the 32-bit output shift registers. The serial bits are
clocked successively into the shift registers until the 32nd bit has been received, the registers
then latch the data and present it on the 32-bit buses (CHANA, CHANB and CHANC) to the
output switches. The data is refreshed in this manner at each scan of the system.