ProSoft Technology MVI56E-MNETC - Manual (Page 119)

MVI56E-MNETC ♦ ControlLogix Platform Reference
Modbus TCP/IP Client Enhanced Communication Module User Manual
ProSoft Technology, Inc. Page 119 of 183
February 3, 2013
Block Request from Module to Processor
Word Offset Description Length
0 Reserved 1
1 1000 to 1049 1
2 to 248 Spare 247
249 1000 to 1049 1
Ladder logic subtracts 1000 from the value contained in word 249 to determine a
block index. This bock index determines which 200-word block of data will be
taken from the ReadData array and placed in the output image to be returned to
the module.
Block Response from Processor to Module
Word Offset Description Length
0 1000 to 1049 1
1 to 200 Output data to preset in module. 200
201 to 247 Spare 47
Event Command Blocks (2000 to 2029)
Note: To use the Event Command Block for polling operations, you need to
configure at least one command in the client even if the command is disabled.
During routine operation, the module continuously cycles through the user-
defined MNET Client x Command List (page 51) for each Client, examining
commands in the order they are listed, and sending enabled commands on the
network. However, the module also has a special command priority queue, which
is an internal buffer that holds commands from special function blocks until they
can be sent on the network.
When one or more commands appear in the command priority queue:
3 The routine polling process is temporarily interrupted.
4 The commands in the command priority queue are executed until the queue
is empty.
5 Then the module goes back to where it left off on the MNET Client x
Command List and continues routine polling.
Event Command blocks send Modbus TCP/IP commands directly from controller
tags by ladder logic to the Client command priority queue on the module. Event
Commands are not placed in the module's internal database and are not part of
the MNET Client x Command List.