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Fieldbus Communications Support
38
890USE19600 April 2004
Data Exchange
Introduction Process image data is exchanged between the STB NIB 1010 NIM and an
INTERBUS fieldbus master in a bit-packed format.
Data and Status
Objects
Data exchange between the island and the INTERBUS master involves three types
of objects:
data objects—operating values the INTERBUS master either reads from the input
modules or writes to the output modules
status objects—module health records sent by I/O modules and read by the
INTERBUS master
echo output data objects—sent by digital object modules to the INTERBUS
master; these objects are usually a copy of the data objects, but they can contain
useful information when a digital output point is configured to handle the result of
a reflex action
Standard Advantys STB I/O modules support all three of the above objects. Basic
Advantys STB I/O modules support only data objects, not status or echo objects.
The following table shows the relationship between different object types and
different module types. It also shows the size of the different objects:
Note: In this discussion, data and words described as input and output are defined
relative to the master. For example, the master receives input data and transmits
output data.
Module Type Objects in the Input Data Image Objects in the Output Data Image
Objects Size Objects Size
digital input data 1 byte or less does not apply
status
1
1 byte or less does not apply
digital output echo output data 1 byte or less data 1 byte or less
status
1
1 byte or less does not apply
analog input channel 1 data 2 bytes does not apply
status
2
1 byte does not apply
channel2 data 2 bytes does not apply
status
2
1 byte does not apply
analog output channel 1
status
2
1 byte data 2 bytes
channel 2
status
2
1 byte data 2 bytes
1
Echo and status information is not available for every module. For example, basic I/O modules do not report this information. Refer
to The Advantys STB Hardware Components Reference Guide (890 USE 172 00) for details.
2
Status information is not available for every analog module. For example, basic analog modules do not report status. Refer to The
Advantys STB Hardware Components Reference Guide (890 USE 172 00) for details.