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MVI56-MCM
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ControlLogix Platform
Configuration as a Modbus Master
Modbus Communication Module
Page 30 of 159
ProSoft Technology, Inc.
July 24, 2008
Label Description
MinCmdDelay
0 to 65535 milliseconds min. time between each commands
Ex: A value of 10 will cause the module to wait 10 milliseconds between
the issuance of each Modbus master command.
CmdErrPtr
Internal DB location to place command error list
RespTO
0 to 65535 milliseconds response timeout for command
RetryCount
Retry count for failed request
ErrorDelayCntr
0 to 65535 Command cycle count if error
InterCharacterDelay
0 to 65535 milliseconds time between characters to signal end of
message
Further clarification for some parameters in table above.
Parameter Description
CmdCount
Command count list 100 = causes the module to look at
MCM.CONFIG.PortX. MasterCommand[0]-[99]. 10 = cause commands
[0]-[9] to be processed. Sets how many registers will be used for error
codes as set in the CmdErrPtr value.
CmdErrPtr
Set Master Command Errors location. Each command will reserve one for
the command error code. See "Verifying Communications" of this manual.
CmdErrPtr value should be within the range of the ReadData array, per
MCM.CONFIG.ModDef of this manual.
RespTO
1000 = 1000 milliseconds (1 second) before it will either reissue the
command (as set in the RetryCount) or if the RetryCount has already
been met, then it will move on to the next command in the list.
ErrorDelayCntr
Sets consecutive commands to that slave will be skipped if a command
has gone into error. For example, if a command to slave 1 has gone into
error (RespTO has elapsed, and RetryCount has been met), the module
will skip the next X number of commands in the list to node number 1.
This can be useful in applications where a slave device is taken offline, as
the module will try the first command to that slave, and then skip the next
X number of commands to that slave so that time is not lost on trying to
poll information from a slave device that is not on the network.
InterCharacterDelay
Sets the Inter Character Delay for the module. Within Modbus RTU a
character gap or quiet time on the line signals the end of the message.
This is typically 3.5 character widths, as specified by the Modbus protocol.
In some Radio or Modem applications, there may be more of a delay
between characters.