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3
Basic Operation
3.1
Software Requirements
No additional network support code needs to be written in order to support the Anybus Com-
pactCom 40 Modbus-TCP, however due to the nature of the Modbus-TCP networking system,
certain restrictions must be taken into account:
•
The total number of ADIs that can be represented on the network depends on their size. By
default, ADIs with instance numbers 1...3839 can be accessed from the network, each with
a size of up to 32 bytes.
•
ADI names, types and similar attributes cannot be accessed viaModbus-TCP. They are
however represented on the network through the built in web server.
•
A network write access of an ADI mapped to process data will result in a corresponding
write access of the process data buffer of the Anybus CompactCom 40 Modbus-TCP.
•
A network read access of an ADI, even if it is mapped to process data, will result in a corre-
sponding Get_Attribute command towards the application.
•
Modbus-TCP reset requests are not supported.
•
Up to 5 diagnostic instances (See Diagnostic Object) can be created by the host applica-
tion during normal conditions. An additional 6th instance may be created in event of a major
fault.
•
Modbus-TCP in itself does not impose any specific timing demands when it comes to acy-
clic requests (i.e. requests towards instances in the Application Data Object), however it is
generally recommended to process and respond to such requests within a reasonable time
period (exactly what this means in practice depends on the implementation and the actual
installation).
•
The use of advanced Modbus-TCP specific functionality may require in-depth knowledge
in Modbus-TCP networking internals and/or information from the official Modbus-TCP
specifications. In such cases, the people responsible for the implementation of this product
is expected either to obtain these specifications to gain sufficient knowledge or limit their
implementation is such a way that this is not necessary.
See also...
•
Application Data (ADIs), p. 13
•
Diagnostic Object (02h), p. 27
•
Anybus CompactCom 40 Software Design Guide, “Application Data Object (FEh)”
For in depth information regarding the Anybus CompactCom software interface, consult the
Anybus CompactCom 40 Software Design Guide.
Anybus
®
CompactCom
™
40 Modbus-TCP
®
Transparent Ethernet Network Guide
SCM-1202-022 1.1