ProSoft Technology 5204SE-MNET-PDPMV1 - Manual (Page 98)

5204SE-MNET-PDPMV1 ♦ ProLinx Gateway Reference
Modbus TCP/IP to PROFIBUS DP-V1 Pass-Through Master User Manual
Page 98 of 235
ProSoft Technology, Inc.
December 22, 2009
4.4 Modicon M340 Variables, Derived Data Types, and Derived Function
Blocks
4.4.1 M340 Modbus Variables and Derived Data Types (DDTs)
The Modbus Derived Data Type (DDT) is a special DDT used by all other DDTs
and Derived Function Blocks (DFBs). This DDT holds all the variables needed to
create a Modbus TCP/IP Client command which the processor can then transmit
to servers on the network. The specific purpose of this DDT is to allow any
parameters or data needed to create a valid PROFIBUS DP Master request to be
passed from the processor to the 5204SE-MNET-PDPMV1 as a Modbus TCP/IP
message, which can then be re-transmitted on the PROFIBUS DP network, if
required.
You can think of the variables in this structure as temporary holding registers.
They will be used by all the other DDTs and DFBs to build and transmit each
required Modbus TCP/IP message. No direct manipulation of these variables
should be required or attempted by any other parts of your application code. The
other imported DDTs and DFBs will make all necessary changes to these
variables for you, as required. The information here is given for reference only.