Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM User Manual

Page 100

Publication AG-UM008C-EN-P - February 2005

3-32 Configuring MicroLogix 1100/1200/1500 Controllers

Figure 3.5 Applying Store and Forward with DF1 Radio Modem Protocol

Figure 3.6 Store & Forward Table for Node 2

Node 4

No Bits

Node 3

1, 2, 4

Node 2

1, 3, 4

Node 1

No Bits

CMD 1

(DST = 4, SRC = 1)

REPLY 1

(DST = 1, SRC = 4)

CMD1

(1st Rebroadcast)

Note 1

(2nd Rebroadcast)

REPLY 1

CMD 1

(2nd Rebroadcast)

(1st Rebroadcast)

REPLY 1

Note 4

Note 2

Note 1 – The link layer of Node 1 blocks the re-transmission of a packet that is received with the SRC byte equal to the
receiving node’s station address. Packets received that originate from the receiving node should never be re-transmitted.

Note 2 – To prevent Node 2 from re-transmitting a duplicate packet, the link layer of Node 2 updates the duplicate packet
table with the last 20 packets received.

Note 3 – The link layer of Node 4 blocks the re-transmission of a packet that is received with the SRC byte equal to the
receiving node’s station address. Packets received that originate from the receiving node should never be re-transmitted.

Note 4 – To prevent Node 3 from re-transmitting a duplicate packet, the link layer of Node 3 updates the duplicate packet
table with the last 20 packets received.

Note 3