Page 263 - Sensors and Control Systems in Manufacturing

Networking of Sensors and Contr ol Systems in Manufacturing
prevent the recirculation of messages. With AbNET, the performance 223
of the proposed network would probably exceed that of a network
that relies on a central unit to route messages. Communications
would automatically be maintained in the remaining intact parts of
the network even if fibers were broken.
For the power system application, the advantages of optical-fiber
communications include electrical isolation and immunity to electri-
cal noise. The AbNET protocols augment these advantages by allow-
ing an economical system to be built with topology-independent and
fault-tolerant features.

4.12 The Universal Memory Network
The universal memory network (UMN) is a modular digital data
communication system that enables computers with differing bus
architectures to share 32-bit-wide data between locations up to 3 km
apart with less than 1 ms of latency (Fig. 4.19). This network makes it
possible to design sophisticated real-time and near-real-time data
processing systems without the data transfer bottlenecks that now
exist when computers use the usual communication protocols. This
enterprise network permits the transmission of the volume of data
equivalent to an average encyclopedia each second (40 Mb/s). Examples
of facilities that can benefit from the universal memory network
include telemetry stations, real-time-monitoring through laser sen-
sors, simulation facilities, power plants, and large laboratories (e.g.,
particle accelerators), or any facility that shares very large volumes of
data. The main hub of the universal memory network uses a reflection
center—a subsystem containing a central control processor (the reflection
controller) and a data bus (the reflection bus) equipped with 16 dual
memory parts. Various configurations of host computers, worksta-
tions, file servers, and small networks or subnetworks of computers
can be interconnected by providing memory speed-bandwidth con-
nectivity. The reflection center provides full duplex communication
between the ports, thereby effectively combining all the memories in
the network into dual-ported random-access memory. This dual-port
characteristic eliminates the CPU overhead on each computer that is
incurred with Ethernet.
The reflection bus carries write transfers only and operates at a
sustained data rate of 40 Mb/s. This does not include address, error
correction, and coordination information, which makes actual uni-
versal memory network bus traffic approach 100 Mb/s. The univer-
sal memory network can be implemented in copper cables for dis-
tances up to 15 m and in fiber optics for distances up to 3 km. A
combination of both for media can be used in the same network. Mul-
tiple reflection centers can be interconnected to obtain configurations
requiring more ports.