ProSoft Technology 5204SE-MNET-PDPMV1 - Manual (Page 14)

5204SE-MNET-PDPMV1 ♦ ProLinx Gateway Functional Overview
Modbus TCP/IP to PROFIBUS DP-V1 Pass-Through Master User Manual
Page 14 of 235
ProSoft Technology, Inc.
December 22, 2009
The DFBs create Modbus TCP/IP Client (Master) commands, which are
transmitted to the ProLinx MNET server (slave) driver. The MNET server
recognizes these special Modbus TCP/IP commands as PROFIBUS DP Acyclic
mailbox messages, strips out the PROFIBUS DP-V1 acyclic mailbox message
parameters contained in the Modbus TCP/IP message, and passes those
PROFIBUS message parameters through to the ProLinx PDPMV1 Master driver
for transmission to the PROFIBUS slave or slaves indicated in the message. Any
response message returned by the a slave to the PDPMV1 Master will be
automatically repackaged as a Modbus TCP/IP message and returned to the
Modicon processor, where the imported DFBs will process it.
This process allows a Modicon processor, using its native Modbus TCP/IP
communication ability, to act as a PROFIBUS DP-V1 Master on a PROFIBUS
network. By using a third-party PROFIBUS DP to PROFIBUS PA Link Coupler
(not supplied by ProSoft Technology), you can extend these PROFIBUS
capabilities even further and communicate with PROFIBUS PA slaves.
2.5 Cyclic Polling and Acyclic Messaging Control Logic
The Application Communication Logic functions of ProSoft Configuration Builder
(PCB) automatically create Variables, DDTs and DFBs that have been
customized to match the PROFIBUS part of your PCB application. These
automatically-created structures and logic give you all the basic building blocks
you need to create an effective Modbus TCP/IP to PROFIBUS DP
communication application.
To complete your PROFIBUS communication application, all you will need to do
is to create your own customized control and sequencing logic to call the PCB-
generated DFBs in a logical, controlled manner. It will be your sequencing logic
that will decide when to call for PROFIBUS cyclic I/O data, status, and diagnostic
updates. Your logic will also decide if and when to trigger any acyclic messages
you may need to send.
To help you create your control and sequencing logic, here are a few principles
to keep in mind.
1 Once you have successfully created and downloaded your PROFIBUS
configuration to the 5204SE-MNET-PDPMV1 gateway, the PROFIBUS DP-
V1 Master driver will automatically begin and maintain normal PROFIBUS
cyclic I/O communications. PROFIBUS cyclic inputs and outputs will
constantly be updated on the PROFIBUS network with no action being
required from the processor. This means that PROFIBUS cyclic data
transfers are asynchronous and separate from whatever communication the
processor may or may not be doing between itself and the 5204SE-MNET-
PDPMV1 gateway.