Omron C120 System Manual page 18

Remote I/O Systems
PC
Master
on Rack
PC
Optical and
Wired Masters
on Rack
the PC. This is achieved by mounting a Remote I/O Master Unit to the CPU
Rack to control I/O points located possibly many kilometers away. Each Master
serves as a 'switching point' for controlling all of the I/O points accessed through
it. These I/O points are accessed through the Master, not controlled by it. All I/O
control comes from the program in the CPU.
More than one Master can be mounted to a single PC, with each Master forming
the starting point of a Remote I/O Subsystem, i.e., a Remote I/O Subsystem
includes one Master plus all of the Remote I/O Units controlled through it.
The Remote I/O Units that can be included in each Subsystem depend on the
specifications of the Master. Masters are available either with optical or wire
specifications. Optical Remote I/O Systems transfer data through optical fi-
ber cables to enable the greatest transmission distance and the greatest resis-
tance to electrical noise. Wired Remote I/O Systems use wire cables which
don't offer as great a distance as Optical Subsystems, but do greatly reduce the
burden of wiring remote I/O and afford greater resistance to noise than inde-
pendently wired I/O points. Both types of Master can be mounted to the same PC
to meet specific distance and noise-resistance requirements.
Remotely Controlled I/O Devices
Label printer
Wired Subsystem
Auto welder
Optical Subsystem
Conveyer
All Remote I/O Systems consist of at least one Remote I/O Master Unit con-
nected in series to one or more Units accessed through it. One of these Units
that is common to most Remote I/O Systems is a Remote I/O Slave Unit.
A Master is mounted to the CPU Rack or an Expansion I/O Rack; a Slave is
mounted to a Backplane to form what is called a Slave Rack. To a Slave Rack is
mounted the same other Units as those mounted to the CPU or Expansion I/O
Rack, with only a few exceptions (e.g., Link Units other than Slaves cannot be
mounted to Slave Racks). The advantage of a Slave Rack is that it can be lo-
cated a considerable distance from the CPU Rack with the only connection re-
quired being a cable running from the Master to the Slave. The actual distance a
Slave Rack can be removed from the Master, as well as the other Units used to
configure a Remote I/O System, depends on the type of Remote I/O System be-
ing used. Collectively, all of the Units connected in a Remote I/O System are re-
ferred to as Remote I/O Units.
This manual describes Optical Remote I/O Systems. Wired Remote I/O Units
are described in the Wired Remote I/O System Manual .
Section
Glue coater
Polisher
Packing machine
1-1
3