Allen-Bradley 1779-KFMR User Manual page 141

Chapter 9
below the application layer of the communication software, the data field
is passed up to the next higher layer where additional fields are defined.
Figure 9.1
Time Critical General Format
Native Fields
Figure 9.1 shows the time-critical message packet format including the
Native fields. The Native fields are those fields common to all message
transmissions in the Native mode. Here we describe these Native fields.