Glossary
relay-based control
The forerunner of PCs. In relay-based control, groups of relays are intercon-
nected to form control circuits. In a PC, these are replaced by programmable cir
-
cuits.
reserved bit
A bit that is not available for user application.
reserved word
A
word in memory that is reserved for a special purpose and cannot be accessed
by the user.
reset
The process of turning a bit or signal OFF or of changing the present value of a
timer or counter to its set value or to zero.
Restart Bit
A bit used to restart a Unit mounted to a PC.
restart continuation
A process which allows memory and program execution status to be maintained
so that PC operation can be restarted from the state it was in when operation
was stopped by a power interruption.
retrieve
The processes of copying data either from an external device or from a storage
area to an active portion of the system such as a display buffer. Also, an output
device connected to the PC is called a load.
retry
The process whereby a device will re-transmit data which has resulted in an er
-
ror message from the receiving device.
rightmost (bit/word)
The lowest numbered bits of a group of bits, generally of an entire word, or the
lowest numbered words of a group of words. These bits/words are often called
least-significant bits/words.
rising edge
ROM
The point where a signal actually changes from an OFF to an ON status.
Read only memory; a type of digital storage that cannot be written to. A ROM
chip is manufactured with its program or data already stored in it and can never
be changed. However, the program or data can be read as many times as de
-
sired.
RS-232C interface
RS-422 interface
scan
An industry standard for serial communications.
An industry standard for serial communications.
The process used to execute a ladder-diagram program. The program is ex-
amined sequentially from start to finish and each instruction is executed in turn
based on execution conditions. The scan also includes peripheral processing,
I/O refreshing, etc. The scan is called the cycle with CV-series PCs.
scan time
The time required for a single scan of a ladder-diagram program.
self diagnosis
A
process whereby the system checks its own operation and generates a warn
-
-
ing or error if an abnormality is discovered.
series
A wiring method in which Units are wired consecutively in a string. In Link Sys
tems wired through Link Adapters, the Units are still functionally wired in series,
even though Units are placed on branch lines.
servicing
The process whereby the PC provides data to or receives data from external de
vices or remote I/O Units, or otherwise handles data transactions for Link Sys
tems.
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OMRON [ OMRON ELECTRONICS LLC ]
