Chapter 1. General
1 - 4
1.3 Terminology
The following table gives a definition of terms used in this manual.
Terms Definition Remarks
Module
A standard element that has a specified function which
configures the system. The devices such as I/O board, which
inserted onto the mother board or base unit.
Example)
CPU module,
Power supply
module,
I/O module
Unit
A single module or group of modules that perform an
independent
Operation as a part of PLC system.
Example)
Main unit
PLC System
A system which consists of the PLC and peripheral devices. A
user program can control the system.
Cold Restart
To restart the PLC system and user programs after all of the
data (variables and programs of I/O image area, of internal
register, of timer of counter) were set to the specified
conditions automatically or manually.
Warm Restart
In the warm restart mode, the power supply Off occurrence will
be informed to the user program and the PLC system restarts
with the previous user-defined data and user program after the
power supply Off.
Hot Restart
After the power went off, the PLC system restores the data to
the previous conditions and restarts in the maximum allowed
time.
I/O Image
Area
Internal memory area of the CPU module which used to hold
I/O statuses.
Watch Dog
Timer
Supervisors the pre-set execution times of programs and
warns if a program is not completed within the pre-set time.
Function
Operation Unit which outputs immediately its operation result of
an input, while four arithmetic operations comparison operation
store their results in the inside of instructions.
Function
Block
Operation Units which store operation result in the inside of
instruction such as timer and counter and use the operation
results which have been stored through many scans.
Direct
Variable
Variables used without the definition of their names and types.
There are I, Q, M areas.
Example)
y%IX0.0.2
y%QW1.2.1
y%MD1234 etc.
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