Reference
MVI56E-MCMR ♦ ControlLogix Platform
User Manual
Modbus Communication Module with Reduced Data Block
Page 160 of 223
ProSoft Technology, Inc.
Block Response from Module to Processor
Word Offset
Definitions
0
9902 or 9912 Command Control ID Number
1
0 = Fail-No Special Commands were added to the Command Queue
>0 = Success - Indicates the number of command control successfully
added to the Command Queue.
Note:
This number should match the Command Count (Word 0 of the
Send Command Control
MSG)
2
Reserved for future use (will always be zero)
3
Reserved for future use (will always be zero)
5
Reserved for future use (will always be zero)
Please note that the status returned in Word 1 indicates only that the command
or commands from the
Send Command Control
MSG was or were successfully
added to the top of the Command Queue as the next command or commands to
be sent. A "Success" result in this data block does not indicate:
Whether the command was successfully sent on the Modbus Network
Whether the Slave received or responded to the command
Whether the Slave's response (in any) was valid
There are many potential reasons why a command might fail after having been
successfully added to the Command Queue. For more details, see Standard
Modbus Protocol Errors or Module Communication Error Codes. But, unlike
Event Commands
, which do not provide any status feedback on actual command
execution, the execution status of commands sent using
Command Control
can
be obtained.
Since these commands are part of the Command List, the execution status of
these commands is available in the
Master Command Error List
. The status
shown in this list will be updated every time the command is executed. Therefore,
once the Command Control MSG was been sent and after a short delay, you can
request the command execution status using a
Get Command Error List
MSG.
See the next section for details.
