ProSoft Technology MVI71-MNET - Manual (Page 32)

MVI71-MNET ♦ PLC Platform Module Configuration
Modbus TCP/IP Interface Module User Manual
Page 32 of 109
ProSoft Technology, Inc.
June 23, 2009
Command List Overview
In order to interface the MVI71-MNET module with Modbus TCP/IP Server
devices, you must construct a command list. The commands in the list specify
the Server device to be addressed, the function to be performed (read or write),
the data area in the device to interface with and the registers in the internal
database to be associated with the device data. The Client command list
supports up to 100 commands.
The command list is processed from top (command #0) to bottom. A poll interval
parameter is associated with each command to specify a minimum delay time in
tenths of a second between the issuance of a command. If the user specifies a
value of 10 for the parameter, the command will be executed no more frequently
than every 1 second.
Write commands have a special feature, as they can be set to execute only if the
data in the write command changes. If the register data values in the command
have not changed since the command was last issued, the command will not be
executed.
If the data in the command has changed since the command was last issued, the
command will be executed. Use of this feature can lighten the load on the
network. In order to implement this feature; set the enable code for the command
to a value of 2.
Commands Supported by the Module
The format of each command in the list is dependent on the Modbus Function
Code being executed.
The following table lists the functions supported by the module.
Function Code Definition Supported in Client Supported in Server
1 Read Coil Status X X
2 Read Input Status X X
3 Read Holding Registers X X
4 Read Input Registers X X
5 Set Single Coil X X
6 Single Register Write X X
7 Read Exception Status X
8 Diagnostics X
15 Multiple Coil Write X X
16 Multiple Register Write X X
22 Mask Write 4X X
23 Read/Write X
Each command list record has the same general format. The first part of the
record contains the information relating to the communication module and the
second part contains information required to interface to the Modbus TCP/IP
Server device.