Rockwell Automation Publication 1789-UM002K-EN-P - January 2015
89
Communicate with Serial Devices
Chapter 4
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.
Normal Poll Group Size
Standard Polling modes only
The number of stations the master station polls after polling all the stations in the priority poll array. Enter 0 (default) to poll the entire array.
Priority Poll Node Tag
Standard Polling modes only
An integer tag array that contains the station addresses of the slave stations you need to poll more frequently.
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
Standard Polling modes only
An array that stores a flag for each of the active stations on the DF1 network.
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
Choose 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
Choose whether the controller should detect duplicate messages. The default is duplicate detection enabled.
Table 5 - Master Station Configuration
Field
Description
