Auto-Zone Control Systems Auto-Zone Basic Systems Installation & Operation (Version 02C) - Manual (Page 103)

Auto-Zone Basic Section 4
Start-Up & Troubleshooting 4-1
Communications
Overview
Perhaps no other portion of the system seems as difficult to diagnose as the communica-
tions loop, yet it really can be quite simple if you understand how it works. In fact, much
of the troubleshooting can be done by simple observation. We will lead you through the
system functions and then provide you with detailed instructions for checking each piece
of equipment. This information is provided as a review and expanded guide to the Auto-
Zone Basic Control System communications. Additional information about the Auto-
Zone Basic Control System communications loop and its associated wiring is contained
in Section 2 of this manual.
How It Works
Auto-Zone uses a token-passing loop architecture, which means in simple terms that an
“electronic message” called a token is passed from controller to controller in a round-
robin fashion. A controller must wait to receive the token before it can send or request
any data. Only one device on each loop is capable of sending the token, and this device is
considered the loop master. The loop master varies depending on the type of system and
the installed options. For the Auto-Zone Basic Control System, there is only one loop
master. The loop master is the Zone Manager. The Zone Manager must be connected to
the zone controllers in order for the communications loop to function. A typical Auto-
Zone Basic Control System communication loop is shown in Figure 4-1.
In order for the loop master to communicate with the various devices on that loop, each
must have a unique address. With the Auto-Zone Basic Control System, each zone con-
troller on the loop must have its own address from 1 to 16. The Zone Manager also has an
address switch that must be set for the system to communicate. For the Basic System
without an optional CommLink connected, the Zone Manager address should be set to 0.
For the Basic System with the optional CommLink attached, the Zone Manager must be
set as address 17 and the CommLink’s jumper switch must be set to single loop opera-
tion.