Page 254 - Sensors and Control Systems in Manufacturing

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Cha p te r

A F o u r B C D E
Independent Standards/
action protocols

Defined Scope of
layers interface
agreement

All integration Requires Function Vendors and
responsibility detailed bridge integrators
of system integrator strategy conform to
integrator understanding standards
based on vendor of vendor
documentation equipment
No RS-232 TCP/IP Specified MAP and
coordination Ethernet ® (and functional other
between Ethernet) interface protocols
integrator
and vendors

FIGURE 4.11 Levels of integration of computer networks.

networks of this type are in common use. Such networks require that
multiple RS-232 interfaces be present on each equipment unit, as is
often the case. Each particular interconnection must be customized
for the two equipment units being considered. Thus, a system inte-
grator not only must decide on the elements of the system and how
they should perform in a functional sense, but also must develop a
detailed understanding of the ways in which RS-232 concepts have
been applied to the particular equipment units used for the network.
The system integrator incurs a substantial expense in achieving the
required interconnections.
It is essential to realize that the RS-232 pseudo-standard only
addresses the ability to transfer serially information bit by bit from
one system element to another. The higher level communications
protocol in Fig. 4.11 is not considered. RS-232 provides the means for
running wires or fiber-optic cables from one element to another in
order to allow digital signals to be conveyed between system ele-
ments. The meaning associated with these bits of information is com-
pletely dependent on the hardware and software implemented in the
system elements. RS-232 is a widely used approach for computer ele-
ments to transfer information. Using RS-232 is certainly much better