Monitoring Transmissions - Allen-Bradley 1779-KFMR User Manual

SOURCE
Packet
2 OK
Packet
Packet
3 OK, 4 OK

Monitoring Transmissions

Figure 6.8 shows an RR response which the transmitter has to discard.
However, after the next data frame, the RR response serves as an
acknowledgment for both data frames. Therefore, no frames are
retransmitted.
Figure 6.8
Message Transfer with an RR Response Discarded
XMTR LINK
1,D2,7
1,RR3
1,D3,7
1,RR???
1,D4,7
1,RR5
If you were to connect a line monitor to the wires between the 1779-KFM
interface and its host computer, you could see:
The link-level commands on circuit AB and their responses on circuit
BA.
The link-level commands on circuit BA and their responses on circuit
AB.
The notation we use here to represent a data frame is:
Chapter 6
HDLC Data Link Layer
RCVR SINK
Not Full
Packet
Not Full
Packet
Not Full
Packet
1,D3,7
6 25