Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 105)

Chapter
10
10Ć1
Full-Duplex Protocol
If you are connecting the 1775–KA module to another Allen–Bradley
communication interface module (such as a 1771–KG, 1775–KA,
1773–KA, or 1771–KE/KF module), then you need not be concerned with
the protocol described here because the modules automatically take care
of it. However, if you are connecting the 1775–KA module to a
computer, then you must program the computer to understand and to issue
the full–duplex protocol described in this chapter or the half– duplex
protocol described in chapter10. Specifically, this chapter outlines the
logic for a full–duplex, input/output driver (transmitters and receivers)
used on the RS–232–C link.
A physical link consists of a cable and associated hardware, such as
transmitter and receiver circuits. Protocol is the set of programming rules
for interpreting the signal transmitted over the physical link by the
hardware devices.
You can connect the 1775–KA module to either of two types of links:
Point–to–point physical link
Multidrop physical link
You can select the 1775–KA module to provide either:
a full–duplex, unpolled protocol for peer–to–peer communication only
a half–duplex, polled protocol for peer–to–peer or master/slave
communication
The type of communication protocol you can use depends on the type of
physical link you have:
For this type of physical ink You can use this communication protocol
a point-to-point link either a peer-to-peer or master/slave communication
a multi-drop broadband MODEM link either a peer-to-peer or master/slave communication
a multi-drop baseband
a master/slave communication MODEM link (because
the link can support only one channel)
General
Definition of Link and Protocol