Allen-Bradley 1779-KFMR User Manual page 169

Chapter 11
PAD Message Set
11 2
passed up from and down to the HDLC data-link layer. At each layer
below the application layer to the communication software, the data field
is passed up to the next higher layer where additional fields are defined.
Figure 11.1
PAD Format in Native Mode
Application Fields
PAD Fields
STS TNS
Native Fields
HDLC Data Link Fields
FLG ADDR
Native Fields
Figure 11.1 shows the Native-mode PAD 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.
Data (Any Format)
238 Bytes Max.
LINK NODE USER
SEL SSQ EXT DATA
x6 FF (From Preceding Layer)
CTL DATA
(From Preceding Layer)
DATA
(from Preceding Layer)
FCS FLG