User manual

IEC61131 User and Reference Manual
April 22, 2008
497
The Master Station Address edit box specifies the Master Station Address. Enter any valid Station
address from 0 to 65519.
 The OK button adds the Master Station Address to the list and closes the dialog. An error is
displayed if the Master Station Address is invalid, if the address is already in the list, or if the
address conflicts with the RTU station address.
 The Cancel button closes the dialog without making any changes.
The RTU Station Address parameter specifies the address of this RTU. It is the source address used
by this DNP driver when communicating with a master station. Each DNP station in a network must
have a unique address, including the Master station. Valid entries for RTU Station Address are 0 to
65519.
The Data Link Confirmation parameter specifies whether or not the RTU requests the underlying
data link transmitting its response to use a high quality service, which generally means that the data
link requires the receiving data link to confirm receipt of all messages.
The Retries parameter specifies the maximum number of times the data link layer will retry sending
a message to the master station. This parameter is only used when responding to a request from a
Master station, when there is no corresponding entry in the Routing dialog for that station. This is
independent of the application layer retries. The valid values for this parameter are 0 - 255. Setting
the value to 0 disables sending retries.
Note: Using data link layer Confirmation and Retries is inherently less efficient than
application layer Confirmation and Retries. Each fragment sent by the Application
layer may require as many as 10 data link layer frames to be sent, each with its own
confirmation message. The data link layer is typically not used for message
confirmation for this reason.
The Data Link Timeout parameter specifies the expected time duration that the master station's data
link layer requires to process and respond to a message from the RTUs data link layer. It is used by
the RTU in setting its time-out interval for master station responses. This value should be large
enough to prevent response time-outs. The value must be kept small enough so as not to degrade
system throughput. The value of this element is dependent on the master station. It is expressed in
milliseconds. Valid values are 10 to 60000 milliseconds. The default value is 500 milliseconds.
 Click the OK button to accept the configuration changes and close the DNP Settings dialog.
 Click the Cancel button to close the dialog without saving any changes.
 Click the Delete button to remove the selected rows from the list. This button is disabled if there
are no entries in the list.
The Allow Duplicate Modbus Addresses checkbox determines if the Modbus I/O database
addresses assigned to the DNP data points must be unique. Check this box if you want to allow more
than one point to use the same Modbus address.