Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 246)

Publication AG-UM008C-EN-P - February 2005
7-20 Configuring Logix Controllers
Table 7.6 Define these parameters when configuring a Logix controller as a slave
station.
Configuring Slave Poll
Timeout The Slave Poll Timeout is only used when the DF1 half-duplex slave is
initiating MSG instructions in ladder logic. This implies that the Master
is most likely configured for Standard Polling Mode. The minimum
Slave Poll Timeout value is dependent on the maximum Master poll
scan rate. Since the Master’s polling and the Slave’s triggering of a
MSG instruction are asynchronous events, it is possible that in the
instant just after the slave was polled, the MSG instruction gets
triggered. This means the MSG instruction will remain queued-up for
transmission until the Master has polled every other slave first.
Therefore, the minimum Slave Poll Timeout value is equal to the
maximum Master poll scan rate rounded up to the next 20 ms
increment.
DF1 Half-Duplex Slave
Diagnostic Counters DF1 Half-Duplex Slave driver status data is stored in the Diagnostic
Counter attribute of the DF1 communication object. You must define a
controller tag to be the destination for this data and copy the system
data to this tag using a GSV instruction. For the required ladder logic,
see page 7-25.
Parameter Description Default
Station Address The station address for the serial port on the DF1 slave. Enter a valid DF1 address
(0 to 254). 0
Transmit Retries The number of times the slave station retries a message after the first attempt before the
station declares the message undeliverable. Enter a value 0 to 127. 3
Slave Poll Timeout Specifies the amount of time the slave station waits to be polled by a master before
indicating a fault. Enter a value 0 to 32767. Limits are defined in 20 ms intervals.
See“Configuring Slave Poll Timeout” for further details. 3000
(60,000 ms)
EOT Suppression Select whether or not to suppress sending EOT packets in response to a poll. The default is
not to suppress sending EOT packets. Do not suppress
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
Minimum Slave Poll Timeout = (maximum Master scan poll rate)