Rockwell Automation 5720 DriveLogix System - Manual (Page 207)

Publication 20D-UM002C-EN-P - November 2003
Communicating with Devices on a Serial Link 9-13
If you choose one of the standard polling modes
The master station polls the slave stations in this order:
1. all stations that are active in the priority poll array
2. one station that is inactive in the priority poll array
3. the specified number (normal poll group size) of active stations in the
normal poll array
4. one inactive station, after all the active stations in the normal poll array
have been polled
Use the programming software to change the display style of the active station
array to binary so you can view which stations are active.
Active station tag Standard polling modes only
An array that stores a flag for each of the active stations on the DF1 link.
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 both 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 in a computer driver. This is the default.
CRC: the controller sends and accepts messages with a 2-byte CRC for error checking. CRC is a more
complete method.
Enable duplicate
detection Select whether or not the controller should detect duplicate messages. The default is duplicate detection
enabled.
This field: Description: