Specifications

Fieldbus Communications Support

31004624 8/2009

Data Exchange

Introduction

This topic discusses the manner in which bit packed process image data is

exchanged between the STB NIB 2212 NIM and an INTERBUS fieldbus master.

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.

Data and Status Objects

Data exchange between the island and the INTERBUS fieldbus master involves

three types of objects:

z data objects—operating values the INTERBUS master either reads from the input

modules or writes to the output modules

z status objects—module health records sent by I/O modules and read by the

INTERBUS master

z 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

The following table shows the relationship between different object types and

different module types. It also shows the size of the different objects:

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 byte or less does not apply

digital output echo output data 1 byte or less data 1 byte or less

status* 1 byte or less does not apply

analog input channel 1 data 2 bytes does not apply

status 1 byte does not apply

channel 2 data 2 bytes does not apply

status 1 byte does not apply

analog output channel 1 status 1 byte data 2 bytes

channel 2 status 1 byte data 2 bytes

*Not available for every module. Check The Advantys Hardware Components Reference Guide (890 USE 172 00)

for relevant modules.