Rockwell Automation 842D-60131331BXA DeviceNet Encoder User Manual - Manual (Page 29)

Configuring a Scanner to Communicate with the Encoder 5-3
For more detail see the Assembly object manufacturer specific
functions in Appendix B.
Polling mode
The standard mode in the master-slave communication is the polling
mode. In this mode the master contacts all bus participants cyclically.
The output data are transmitted to the slaves and the input data are
read from the slaves over the course of one scan.
Because the 842D is an Input Device, output data from the master is
ignored. The Poll Command is used to trigger the transmission of
return input data in the response message.
COS mode / Cyclic mode
In Change of State (COS) mode, the encoder sends input data if the
value of one of the data components changes or at the Heartbeat Rate
(See Figure 5.4, Edit I/O Parameters Dialog Box - COS).
In addition, a Cycle Time is used to trigger the transmission of the
input data. This is done after the internal Cycle Time period has
elapsed, no matter if the value of one of the data components has
changed.
Additionally, a time delay (inhibit time) in the range of 1 msec. to
65,535 msec. can be configured to reduce the bus load.
When getting a trigger only from the "cam state" or "Flag" data
components by using Instance 2 or 4 in a COS connection, you should
set the value of "COS / Hyst." (attr. 11) to "0" (zero) to avoid a trigger
from the data component "position value" (see Appendix B).
In Cyclic mode the encoder only sends input data after the internal
Cycle Time period has elapsed.
Bit Strobed mode
The Bit_Strobe Command sends one bit of output data to each Slave
whose node address appears in the Master's scan list.
Because the 842D encoder is an Input Device, the output data bit is
ignored. The Bit Strobe Command is only used to trigger a
transmission of return input data in the response message.