Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 236)

Publication AG-UM008C-EN-P - February 2005
7-10 Configuring Logix Controllers
ACK Timeout Specifies the amount of time you want the controller to wait for an acknowledgment to
its message transmission. Enter a value 0 to 32767. Limits are defined in 20 ms intervals. 50 (1000 ms)
Polling Mode If you want to receive:
•
only one message from a slave station per its turn, choose STANDARD (SINGLE
MESSAGE TRANSFER PER NODE SCAN). Choose this method only if it is critical
to keep the poll list scan time to a minimum.
•
as many messages from a slave station as it has, choose STANDARD (MULTIPLE
MESSAGE TRANSFER PER NODE SCAN)
Master Transmit If you want the master station to:
•
send all of the master station-initiated MSG instructions to the slave stations
before polling the next slave station in the poll list, choose Between Station
Polls. This method makes certain that master station-initiated messages are sent
in a timely and regular manner (after every slave station poll).
•
only send master station-initiated MSG instructions when the master’s station
number appears in the polling sequence; choose In Poll Sequence. With this
method, sending master station-initiated messages are dependent upon where
and how often the master station appears in the poll list. To achieve the same
goal as the Between Station Polls method, the master-station’s address would
have to appear after every slave-station’s address.
Between
Station Polls
Normal Poll Node Tag An integer array (list in the format example) that contains the station addresses of the
slave stations (in the order in which to poll the stations).
Create a single-dimension array of data type INT that is large enough to hold all the
normal station addresses. The minimum size is three elements.
This tag must be controller-scoped. The format is:
list[0] contains total number of stations to poll
list[1] contains address of station currently being polled
list[2] contains address of first slave station to poll
list[3] contains address of second slave station to poll
list[n] contains address of last slave station to poll
Normal Poll Group Size The number of normal stations the master station polls after polling all the stations in
the priority poll array. 0
Priority Poll Node Tag An integer array that contains the station addresses of the slave stations you need to
poll more frequently (in the order in which to poll the stations).
Create a single-dimension array of data type INT that is large enough to hold all the
priority station addresses. The minimum size is three elements.
This tag must be controller-scoped. The format is:
list[0] contains total number of stations to be polled
list[1] contains address of station currently being polled
list[2] contains address of first slave station to poll
list[3] contains address of second slave station to poll
list[n] contains address of last slave station to poll
Active Station Tag An array that assigns a bit to every potential DF1 address (0 to 254). The bit is set if the
station is active and cleared if the station is inactive.
Both the normal poll array and the priority poll array can have active and inactive
stations. A station becomes inactive when it does not respond to the master’s poll.
Create a single-dimension array of data type SINT that has 32 elements (256 bits). This
tag must be controller-scoped.
Error Detection Select BCC or CRC error detection.
Configure all stations to use the same type of error checking.
BCC: the controller sends and accepts messages that end with a BCC byte for error
checking. BCC is quicker and easier to implement, but does not detect as many errors as
CRC.
CRC: the controller sends and accepts messages with a 2-byte CRC for error checking.
CRC is a more effective error detection algorithm. BCC
Enable Duplicate Detection Select whether or not the controller should detect and ignore duplicate messages. Enabled
Parameter Description Default