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4-2 Field Control™ Genius® Bus Interface Unit User’s Manual
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October 1999 GFK-0825F
4
BIU Data Handling at the I/O Station
The BIU manages all movement of data within the I/O station and between the I/O station and the
Genius bus. The BIU scans the I/O modules in the station, exchanges data with the host, and can
manage the exchange of data between a Micro Field Processor and other modules in the station. In
addition to its regular I/O scanning capabilities, the BIU can also selectively transfer specific data
groups from one intelligent module in the station to another.
All of the data for the I/O station, whether it is data that is exchanged on the Genius bus or local
data, utilizes the BIU's four I/O data memories.
The BIU has 256 bytes of memory available for each of the four types of data (discrete inputs and
outputs, data types I and Q, and analog inputs and outputs, data types AI and AQ). During BIU
configuration, data for individual modules is assigned to specific areas of this memory.
BIU Memory
Type
Typically Used For Amount Available
in BIU
Highest Available
Reference Address
I discrete inputs, and status data from
intelligent modules
256 bytes 65535
Q discrete outputs, and fault clearing for
intelligent modules
256 bytes 65535
AI analog inputs 256 bytes 9999
AQ analog outputs 256 bytes 9999
Data can be configured anywhere within the BIU's available memory. If the data will be exchanged
on the network bus, data must be assigned to contiguous memory locations, as explained later.
The following paragraphs describe the types of data the BIU exchanges with conventional I/O
modules and intelligent I/O modules.