Configuration as a Modbus Master MVI56-MCM ♦ ControlLogix Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 47 of 159
July 24, 2008
4.5.2 Event Command
Similar to command control, event command will also allow the user to add
commands directly to the command queue, interrupting the normal polling
sequence of the module. Unlike command control, event commands do not
return an error code into the location defined by the
MCM.CONFIG.PortX.CmdErrPtr value but Event Commands do not have to be
defined in the regular command list.
Event command is a way of adding a command to the top of the MVI56-MCM
modules command queue that is not defined within the command list.
Within an Event command block, the user is defining a Modbus command to add
to the queue. Special consideration must be taken if the command is a write
command, as the user must make sure that the block within the module that
contains the data to write to the slave contains that latest value from the
WriteData tag that corresponds to the Event Command.
Below is the structure of the EventCommand block.
Parameter Value Description
EventCmdTrigger 1 1 = trigger the event command
EventCmdPending Used = EventCommand is executed once
PortNumber 1 Module port # to send command out to
SlaveAddress 1 Modbus Slave ID command to be issued to
InternalDBAddress 1100
1100 will place the data read into
MCM.DATA.ReadData[100]
PointCount 10
Consecutive register/bits to read or write with the
command
SwapCode 0 Swap code used with command
ModbusFunctionCode 3 FC 3 is read 4xxxx holding registers
DeviceDBAddress 276
Address in the slave device to read. With FC3,
DeviceDBAddress of 276, the module will read
starting at address 40277 in the slave device
EventCmdStatusReturned Return value of 0 = Fail, 1 = Success
EventBlockID
Block ID number for the module to recognize the
event command, slave address, and port number
to send the command out
The ladder logic used for the Event Command blocks is contained in
_WriteControl rung 5 and _ReadControl rung 4 within the sample ladder file.
To Next Page
Loading...
Need help?
General