Multilevel Systems - Omron C120 System Manual

Multilevel Systems

2-2 Multilevel Systems
10
There is no reason that a Remote I/O System must remain restricted to one Mas-
ter or to either wired or optical communications. PCs support multiple Masters,
some of which can be Wired and some of which can be Optical.
If there is more than one Master mounted under the control of a single CPU,
each Master forms the beginning of a Remote I/O Subsystem. Although the
number of Subsystems supported by each PC is limited, each Subsystem can
be considered independently from the others as long as the total capacity of the
PC is not exceeded. It is important to note that although both Wired and Optical
Masters can be controlled by the same CPU, Optical and Wired Remote I/O
Units cannot be combined in the same Subsystem, i.e., Optical Masters can be
connected only to Optical Slaves, Optical I/O Units, and I/O Link Units; Wired
Masters can be connected only to Wired Slaves, Remote Terminals, and I/O Ter-
minals.
In the example on the next page, two CPU Racks are used. The one in the upper
left corner controls two Remote I/O Subsystems, one Wired and one Optical.
The Optical System contains an I/O Link to the other CPU Rack (at the right),
which has one Remote I/O Subsystem controlled by it.
The Optical I/O Unit, Slave Rack, and Expansion I/O Rack beneath the CPU
Rack at the right are controlled through the Optical Master on this CPU Rack.
This Optical Master also connects the CPU to the C20 I/O Link Unit.
Another aspect of Remote I/O Systems demonstrated by this diagram is the
presence of Expansion I/O Racks, both connected to a CPU Rack and to Slave
Racks. Although normally not shown in system diagrams for Link Systems, Ex-
pansion I/O Racks can be used to increase the number of I/O Units mountable at
any one location.
Section 2-2