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47Chapter 3 Remote I/O Scanner Operation
Input Data Sent by the Remote I/O Scanner
When the Remote I/O Scanner has its turn on the bus, it sends one input data message
containing the latest values for all configured discrete inputs followed by all configured
analog inputs. Because they are broadcast (like all Genius inputs), they can be
obtained by any Bus Controller on the bus.
Input Data Message
(up to 128 bytes)
discrete inputs analog inputs
Configured %I Length Configured %AI Length
%AI starting reference data%I starting reference data
To CPU
The lengths of each portion are equal to the lengths of %I and %AI data selected when
configuring the Remote I/O Scanner. Either may be zero.
The discrete inputs appear in the input message in the same sequence as their
assigned input references. Each discrete input module occupies one byte per eight
circuits.
The analog inputs are also in the same sequence as their assigned input references.
Each analog input module occupies two bytes (one word) for each analog channel.
The Remote I/O Scanner sends this data from its internal %I and %AI memories,
beginning at the start locations selected during remote drop configuration of the
Remote I/O Scanner.
How the host handles this data depends on the host type:
A Series 90–70 PLC places the data in the %I and %AI references selected during
PLC configuration. These must be the same references selected during Remote I/O
Scanner configuration.
A Series Six or Series Five PLC places the data into I/O table or register memory.
For a new Remote I/O Scanner, a beginning address in Series Six or Series Five I/O
Table memory can be entered by Logicmaster 90 configuration of the Remote I/O
Scanner. To assign references in register memory instead, or to change a
previously–entered I/O table assignment, a Hand–held Monitor must be used.
A host computer places the data into the input table segment that corresponds to
the Device Number of the Remote I/O Scanner.
Chapter 9 explains how each of these host devices handles the data it exchanges with a
Remote I/O Scanner.