Metso Automation MAX Controls
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Chapter 1
DPU Bus Basics,
an Introduction
Overview
In a maxDNA system, DPU Bus Modules (DBMs) and Models PDP 001 and
PDP 100 Series Distributed Processing Units (DPUs) communicate with
each other over a DPU Bus, consisting of electrical and possibly optical
cable.
The physical network is a 500,000 bits-per-second, half-duplex, hybrid
optical/electrical redundant communications link.
DPU Bus physical components include DPU Bus processors, modems,
optical and electrical cables, terminators, and Optical/Electrical Interfaces
(OEIs).
Use OEIs to connect electrical DPU Buses with optical DPU Buses. OEIs
may also be used to extend electrical cables over longer distances and as
repeaters to extend optical cable lengths beyond 6,600 feet. (nominally 2
km). See "Understanding OEIs."
All components exist in pairs, providing clockwise (CW) and
counterclockwise (CCW) data paths. The DPU Bus design uses two totally
redundant paths for communication. If one path fails, the other will handle
all communication tasks with no loss of communication or DPU Bus
performance.
All messages traverse both the CW and CCW optical data paths allowing the
receiver to use the first message to arrive. Thus, the global network is
immunized against message loss due to any single cable break and is
tolerant, in many cases, of multiple cable breaks.
Devices assigned to a given DPU Bus, DPUs and DBMs, are referred to as
stations. They are configured and defined using maxTOOLS accessible from
a maxSTATION. Each station is identified with a unique address and
granted access to the DPU Bus by means of a token-passing procedure.