ProSoft Technology MVI71-MNET - Manual (Page 59)

Reference MVI71-MNET ♦ PLC Platform
User Manual Modbus TCP/IP Interface Module
ProSoft Technology, Inc.
Page 59 of 109
June 23, 2009
Server Specifications
The MVI71-MNET module accepts Modbus function code commands of 1, 2, 3,
4, 5, 6, 8, 15, 16, 17, 22 and 23 from an attached Modbus Client unit. A port
configured as a Modbus server permits a remote Client to interact with all data
contained in the module. This data can be derived from other Modbus server
devices on the network, through a Client port, or from the ControlLogix
processor.
Client Specifications
A port configured as a virtual Modbus master device on the MVI71-MNET
module actively issues Modbus commands to other nodes on the Modbus
network. One hundred (100) commands are supported on each port. Additionally,
the master ports have an optimized polling characteristic that polls slaves with
communication problems less frequently. The PLC processor can be
programmed to control the activity on the port by actively selecting commands
from the command list to execute or issuing commands directly from the ladder
logic.
5.2 Functional Overview
This section describes how the MVI71-MNET module transfers data between
itself and the processor, and how it implements the Modbus TCP/IP protocol.
5.2.1 General Concepts
The following discussion explains several concepts that are important for
understanding the operation of the MVI71-MNET module.
Module Power Up
On power up the module begins performing the following logical functions:
1 Initialize hardware components
o
Initialize PLC backplane driver
o
Test and Clear all RAM
o Initialize the serial communication ports
2 Initialize the TCP/IP Stack and Ethernet interface module
3 Read configuration for module from MNET.CFG file on Compact Flash Disk
4 Initialize Module Register space
5 Enable Server Drivers
6 Enable Client Driver
After the module has received the configuration, the module will begin
communicating with other nodes on the network, depending on the configuration.