Schneider Electric Processor Adapter - Manual (Page 173)

Using the I/OBus Port
870 USE 101 10 V.2 173
How I/OBus Works
Introduction This section describes how signals are passed and how data is transferred in an
I/OBus network.
How Signals Are
Passed I/OBus operates as a logical ring, with signals being passed by the master over a
remote bus cable to each slave device in series. The slaves return signals to the
master over the same cable.
How Data is
Transferred The I/OBus functions as a logical shift register. The application’s entire data stream,
originating at the master, is transferred serially from slave to slave down the remote
bus. Each slave regenerates the entire stream before passing it on. As a slave
handles the stream data, it extracts the portion that is assigned to it and adds any
output data to the stream.
Transmission
Speed Data is transmitted at 500 kbits/s.
Amount of data The number of 16 bit words in the data stream is dependent on the processor
model:
Model Max Input Words Max Output Words
171 CCS 760 00 128 128
171 CCC 760 10 256 256
171 CCC 960 20 256 256
171 CCC 960 30 256 256
Note: Processors that support IEC are limited to a maximum number of 1408
used I/O points, regardless of the number of modules.