Rockwell Automation 1756-L6x_L7x ControlLogix System User Manual - Manual (Page 106)

106 Rockwell Automation Publication 1756-UM001O-EN-P - October 2014
Chapter 6 Serial Communication on 1756-L6x Controllers
DF1 Radio Modem Protocol Your ControlLogix controller includes a driver that lets it communicate over the
DF1 Radio Modem protocol. The DF1 radio modem driver implements a
protocol, optimized for use with radio modem networks, that is a hybrid between
DF1 full-duplex protocol and DF1 half-duplex protocol, and therefore is not
compatible with these protocols.
Figure 19 - DF1 Radio Modem Network Example
Like DF1 full-duplex protocol, the DF1 radio modem lets any node initiate to
any other node at any time (that is, if the radio modem network supports full-
duplex data-port buffering and radio-transmission collision avoidance). Like
DF1 half-duplex protocol, a node ignores any packets received that have a
destination address other than its own, except for broadcast packets and passthru
packets.
Unlike DF1 full-duplex or DF1 half-duplex protocols, the DF1 radio modem
protocol excludes ACKs, NAKs, ENQs, or poll packets. The CRC checksum
verifies Data integrity.
DF1 Radio Modem Advantages
The primary advantage of using the DF1 radio modem protocol for radio
modem networks is in transmission efficiency. Each read/write transaction
(command and reply) requires only one transmission by the initiator (to send the
command) and one transmission by the responder (to return the reply). This
IMPORTANT The DF1 radio modem driver is used only among devices that support and
are configured for the DF1 Radio Modem protocol.
Additionally, there are some radio modem network configurations that do
not work with the DF1 radio modem driver. In these configurations,
continue to use DF1 half-duplex protocol.
Modem
Modem
Modem
Modem
RS-232
EtherNet/IP Network