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Glossary
A Host Link Unit that mounts onto a Rack, and not directly to the CPU.
baud rate
Transfer speed between two devices in a system measured in bits per se-
cond. For example, an optical sensor might be configured to send its infor-
mation to the FIT at 9600 baud. It is important for both of the devices to be
set to the same baud rate.
bit
The smallest piece of information that can be represented on a computer. A
bit has the value of either zero or one, corresponding to the electrical signals
ON and OFF. A bit is one binary digit.
CPU Rack
Part of a Rack PC, the CPU Rack contains the CPU, a Power Supply, and
other Units.
Cutoff frequency
The maximum frequency that can pass through a lowpass filter; frequency
components higher than the cutoff frequency are blocked.
data area
An area in the PC’s memory that is designed to hold a specific type of data,
e.g., the LR area is designed to hold common data in a PC Link System.
Expansion I/O Rack
Part of a Rack PC, an Expansion I/O Rack is connected to a CPU Rack to
increase the number of slots available for mounting Units.
flag
A bit that is turned ON and OFF automatically by the system in order to pro-
vide status information.
Lowpass filter
Lowpass filters block the high-frequency components contained in voice sig-
nals.
PC
An acronym for Programmable Controller.
PROM Writer
A PROM Writer is a device used to write data to ROM, PROM, and EPROM
storage chips.
RAM
[R(andom) A(ccess) M(emory)] RAM will not retain data when power is dis-
connected. Therefore data should not be stored in RAM
RS-232 interface
An industry standard connector for serial communications.
scan time
The total time it takes the PC to perform internal operations, i.e., reset the
watchdog timer, read the program, receive input data, send output data, and
execute instructions. Scan time is monitored by the watchdog timer within the
PC, and if it takes longer than a certain specified amount of time, an error
message may be generated, or the CPU may just stop. Scan times will differ
depending on the configuration of the system.
Unit
In OMRON PC terminology, the word Unit is capitalized to indicate any prod-
uct sold for a PC System. though most of the names of these products end
with the word Unit, not all do, e.g., a Remote Terminal is referred to in a col-
Rack-Mounting Host Link
Unit
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