MVI56-MCM ♦ ControlLogix Platform Configuration as a Modbus Master
Modbus Communication Module
Page 46 of 159 ProSoft Technology, Inc.
July 24, 2008
4.5.1 Command Control
Command Control will give you the ability to issue a command already defined in
the master command list (but disabled) and enable that command for a single
pass. Command Control has a distinct advantage over event command in that it
will still return an error code for that command as setup in
MCM.CONFIG.PortX.CmdErrPtr. Up to 6 commands may be enabled at the
same time. The configuration of the command control is done using the following
object in the ladder logic.
The following configuration will place 6 commands into the command queue.
MCM.CONFIG.Port1MasterCmd[0]- MCM.CONFIG.Port1MasterCmd[5] will be
enabled with this configuration. Error codes for each individual command will be
returned into the Error Status table.
Tag Value Description
TriggerCmdCntrl 1 1 will execute the command control
NumberOfCommands 6 Number of commands per block
PortNumber 1 MVI56-MCM port number (master)
CommandIndex[0] to [5] 0 to 5
Stores the command index for command control
block
CmdsAddedToQueue
Number of commands added to queue. This is the
confirmation that the command control block has
completed successfully
CmdControlBlockID
Temporary variable to calculate control block ID
number
CmdCntrolPending
Aux. control command - prevents a second request
before acknowledgement is received
Note: The ladder logic necessary for the successful execution of this block is contained in the
_WriteControl ladder file, rung 4, and in the _ReadControl ladder file, rung 2.
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