ProSoft Technology MVI56E-SIE - Manual (Page 144)

Reference MVI56E-SIE ♦ ControlLogix Platform
User Manual Client Communication Module
Page 144 of 168 ProSoft Technology, Inc.
September 6, 2012
Command Control (Blocks 5001 to5016)
Note: Command Control is not needed for normal Siemens Industrial Ethernet
command list polling operations and is needed only occasionally for special
circumstances.
During routine operation, the module continuously cycles through the user-
defined SIE Client x Command List (page 49) 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:
1 The routine polling process is temporarily interrupted.
2 The commands in the command priority queue are executed until the queue
is empty.
3 Then the module goes back to where it left off on the SIE Client x Command
List and continues routine polling.
Command Control blocks place commands into the module’s command priority
queue. Command Control is used with commands already defined in the SIE
Client x Command List.
Commands in the SIE Client x Command List may be either enabled for routine
polling or disabled and excluded from routine polling. A disabled command has
its bit in the SIE.CONTROL.CmdControl.WriteCmdBits controller tag set to zero
(0) and is skipped during routine polling. An enabled command has its bit in the
WriteCmdBits controller tag set to one (1) and is sent during routine polling.
However, Command Control allows any command in the predefined SIE Client x
Command List to be added to the command priority queue, whether it is enabled
for routine polling or not.
Command Control also gives you the option to use ladder logic to have
commands from the SIE Client x Command List executed at a higher priority and
out of routine order, if such an option might be required in special circumstances.
A single Command Control block request can place up to 16 commands from the
SIE Client x Command List into the command priority queue.