Allen-Bradley 1779-KFMR User Manual page 92

Network Packet
SOURCE
Status
Software
SOURCE XMTR
Packet
3 OK
Figure 6.4 represents the protocol environment with the source and
transmitter at one end of the link and the receiver and sink at the other end
of the link.
Figure 6.4
Protocol Environment
Path 1
XMTR
A
Path 2
Hardware
Each of the following figures shows a sequence of events that can occur
between the source and transmitter at one end of the link and the receiver
and sink at the other end of the link. To represent a frame, we show its
address, its link-level command or response, its send sequence number if
applicable, and its receive sequence number if applicable. For example, a
frame shown as 1,D3,7 is a data frame with an address of 1, a send
sequence number of 3, and a receive sequence number of 7. We represent
line noise during a frame transmission by ???. Time is represented as
progressing from top to bottom. Figure 6.5 shows normal message
transfer.
Figure 6.5
Normal Message Transfer
LINK
1,D3,7
1,RR4
Chapter 6
HDLC Data Link Layer
Network Packet
RCVR
B
Full
Software
RCVR SINK
Not Full
Packet
SINK
6 23