Omron SYSMAC PLC Basic Technical Manual
Technical Guide for PLC Basic
CSM_PLC Basic_TG_E_1_1
Introduction
This guide will describe the terminology needed for basic operation of the SYSMAC PLC (Programmable Controller), for clients new to our PLCs.
This guide does not cover technical details regarding the setting of the FA System or PLC programming after purchase.
I/O Refresh
With the PLC (Programmable Controller), commands from user programs designed by the client are executed one by one and processed by
reading and writing information in the internal PLC memory area (At OMRON, we call this the "I/O Memory").
At the same time, packages of data from sensors/switches that are directly connected to the basic I/O unit are exchanged with data in the PLC
internal I/O Memory, at specific times. This process to totally exchange external data and internal I/O memory data is called "I/O Refresh
Operation".
It is important to know the timing by which the I/O Refresh will be executed when considering the operation of the FA System and User Programs
designed by the client. In the case of the SYSMAC PLC, this I/O Refresh operation is performed immediately following the execution of all other
commands. (See Figure below)
PLC
Basic I/O Unit
or built-in I/O
External Data
PLC
Processing Cycle
Common Processing
(Self-Diagnosis)
Execute Program
I/O Refresh
Peripheral Servicing
Inside PLC (CPU Unit)
I/O Memory
Read/Write
00000000
00000000
11011000
00111010
10101001
Change (after all
commands executed)
01010100
01101010
11001010
10111011
10001101
Refresh with external devices
Package
Exchange
(Sensor, Switch, Actuator etc.)
Cycle Time
In terms of the PLC processing cycle, the cycle time is the time from the execution (commencement) of the I/O Refresh operation to the execution
(processing) of the following I/O Refresh.
The cycle time includes time for overhead processing (self-diagnosis), execution of user programs, I/O Refresh processing and the processing of
peripheral services.
• When the cycle time is long, the cycle for updating data from outside of the PLC and the I/O response time are also longer, making it impossible
to implement changes that are input at a rate faster than the cycle time.
• When the cycle time is short, I/O response time is also shortened, which allows high speed processing.
• As the cycle time changes, the command execution cycle and I/O response times also change.
In the case of the SYSMAC PLC, the cycle time can be requested in the following manner:
Cycle Time = Overhead Processing Time + Total Command Execution Time + I/O Refresh Time + Peripheral Service Time
The calculation methods for each execution time for the SYSMAC PLC are included in the product manual.
1
Interrupt Tasks
Normally, user programs are executed in order along with the processing of the I/O Refresh etc., within the PLC processing cycle (See
"I/O Refresh").
Interrupt Tasks however are executed in precedence to this processing cycle. In the event that certain interrupt conditions are met, the processing
cycle will be suspended and the interrupt tasks will be executed first.
(The SYSMAC PLC sometimes refers to the "Interrupt Tasks" as "Interrupt Programs", but here we shall use "Interrupt Tasks", the terminology
used in the CS/CJ Series manuals)
For example, in the case of the CS/CJ Series, Interrupt Tasks can include power Off interrupt, Scheduled Interrupts, I/O Interrupts, Periodic
Interrupts based on the internal timer, and External Interrupts.
Major Interrupt Tasks Details
Power Break Interrupt Tasks Executed during a power break.
Scheduled Interrupt Tasks Executed based on a specific schedule.
I/O Interrupt Tasks Executed at the start-up of a connected Interrupt Input Unit.
External Interrupt Tasks
Executed when requests are received from the Special I/O unit, the CPU Bus Unit, and the INNER Board (only for CS
Series).
I/O Allocation
In order for user programs to utilize I/O signals from the I/O Units mounted to the PLC, it is necessary to first assign an address within the PLC I/
O Memory.
The assignment of I/O Memory to the input or output from these units within the PLC is known as I/O Allocation. The CPU Unit uses this I/O
Allocation information in the operation of I/O Refresh with connected units.
In the case of SYSMAC PLC, this I/O Allocation information is recorded in the PLC in the "Registered I/O Table". This "Registered I/O Table" can
be created by either automatically registering online with programming tools utilizing information from the unit built-in to the PLC, or by using
programming tools to design offline and then automatically registering by transmitting the I/O table to the PLC. (Some devices may not require the
creation of a Registered I/O Table, and others may not support the offline design of I/O Tables.)
● Online Automatic Registration
CX-Programmer or
Programming Console
"Create I/O Table"
Operation
● Offline Automatic Registration
Type and locations of
the Mounted Units
CX-Programmer
Edit Registered I/O Table
"Create I/O Table"
Operation
Registered I/O Table
SYSMAC CJ/CS Series
Type and Location
of Mounted Units
I/O UnitsCPU Unit
I/O UnitsCPU Unit
SYSMAC CJ/CS Series
2
CPU Unit Memory Area
The PLC Unit utilizes a variety of different data including user programs, I/O Memory data and comments, CPU Unit and Special I/O units
Parameters, and Registered I/O Table information etc.
All of this data that is used by the PLC is stored in the memory area within the CPU unit.
The SYSMAC PLC has the following types of Memory Areas, which is backed up by a battery.
In the case of the SYSMAC CS/CJ Series, the content of the Memory Area is backed up using flash memory, which means that even if battery
power fails, any user programs and parameter area data will not be lost.
● User Program Area
This records user programs designed by the client.
● I/O Memory Area
This Area is accessed by command operands. It records information such as the CIO, Internal I/O Area, holding area, auxiliary area, DM Area,
EM Area, Timer Completion Flags/Present Value, Completion Flag/Present Value, Task Flags, Index Register, Data Register, Condition Flags,
Clock Pulse, etc. The data in the I/O Memory Area locates in or is in areas in which the contents are cleared every time the power is turned
back on, and areas in which prior information is retained. (In some areas you can select whether to clear or retain.)
● Parameter Area
This contains all of the information regarding initial parameters used by the PLC.
It records information such as the PLC System Parameters, Registered I/O Table, Routing Table, and PLC Setup for CPU Bus unit.
3
Technical Guide for PLC-based Process Control
CSM_PLC Process_TG_E_1_1
What is the OMRON PLC-based Process Control?
OMRON PLC-based Process Control system is based on the SYSMAC CS/CJ PLC Series. By adding PLC-based Process Control units to the
basic system configuration, PLC process control functions can be simply added on to the basic functions already installed in the PLC.
Thus, it can be used for devices that it is compatible with such process control system in which DCS was used before or devices in which several
controllers were used combined.
With the PLC Installation System, analog processing is carried out by the loop control section or the loop control unit/board (hereafter "loop
controller"), and ladder processing is handled by the CPU. Communication between the two sections is made using bits of memory. Since the
analog processing and ladder processing can be completely separated and the program is more simple than a ladder only program, the
engineering process to construct the system is facilitated.
System configuration of PLC-based process control
The loop controller does not have an external analog I/O or an external contact I/O function.
It is used together with such a unit that has the interface function including an analogue I/O unit, as shown in the diagram below.
Programming
/Monitor PC
4 to 20 mA
PLC
4 to 20 mA
4 to 20 mA
4 to 20 mA
Compensating
Leadwire
Thermo
Couple
4 to 20 mA
PT or HMI
Software
Sensor
Also, when programming, in addition to the programming software for the CPU Unit (CX-Programmer, additional programming software (CXProcess) will be required to create Function block data. And in order to monitor and alter settings during operation, a HMI section will also be
required, in combination with the application in use.
Program Creation Section
Application Section
HMI Section
Operation/Display
Section
Control
Section
Signal I/O Section Analog I/O, Digital I/O, Pulse Input
Signal Conversion (Signal Conditioner)
Field Device Sensor, Actuator
Loop Control Section Function Block (FBD), Sequence Table, Step ladder
Sequence Control
Section
Flow rate Sensor
Operation/Display Screen Creation
Control Block/Sequence Creation
Batch management, brand management, remote
surveillance (Web)
Data gathering, data analysis
Meter screen, graphics screen, trends,
Warning history, operational history, operational guide
Ladder, FB (Ladder/ST Language) CS/CJ Series CPU
Temperature, Current/Voltage, Isolator, Pulse,
Distributor
Capacitive
Flow Rate
Sensor
Process
CX-Process Tool
CX-Programmer
Third Party Products etc
CX-Process Monitor Plus
NS Series etc.
Loop Controller
Loop Control Board/Unit
or Process CPU/Loop CPU
(
Loop Control Section
Process/Analog I/O Unit
Digital I/O Unit etc.
)
1
Installation of PLC Control Panel
CSM_PLC Installation_TG_E_1_1
Introduction
In order to ensure the reliability and security of the system, prior to the design of the system it is important to make certain that the conditions in
which it will be installed is well understood.
Basically, the stresses on the PLC system (temperature, humidity, vibrations, shocks, corrosive gases, overcurrent, noise etc.) need to be reduced
as much as possible. However, the extent to which measures need to be taken in this regard will depend upon the likelihood of problems arising,
the conditions in which the system is installed, and the cost of implementing measures. By taking advanced measures to prevent problems, the
reliability of the system can be improved, and in the long-term the operation rate can also be increased.
For the individual specifications of each unit, please see the respective user manuals.
Installation/Conditions of PLC Control Panel
The following describes the environmental conditions and measures to be taken for the installation of the PLC control panel (hereafter, "the panel")
■Temperature
Based on the operating temperature of the element parts of the PLC,
the operating temperature for the system is generally between 5°C
and 40°C. At the same time, with both forced and natural cooling of
the panel, the fact that it is miniaturized to save space means that
from our experience the temperature of the panel is sometimes 10°C
to 15°C higher than the ambient temperature of the room. As such, it
is important that the following measures be taken depending on the
installation site and the temperatures being generated to make
certain that the panel's internal temperature does not exceed the
range of the unit operating temperature, and to provide a sufficient
margin for the range of operating temperature.
● High Temperature (see Figure 1)
1Natural Cooling (Natural draft at the top and bottom of Panel)
When installing the panel, it is optimal not to make use of
cooling devices such as fans and coolers. The following are
important points in the installation of the PLC.
• Do not install in the upper part where the warm air in the panel
stagnates
• In order to ensure ventilation space, maintain a sufficient
distance from other machinery, wiring ducts etc around the
panel
• Do not install in positions other than those specified (for
example upside down), which can lead to the generation of
abnormal heat within the PLC
• Do not install directly above devices that generate heat such as
heaters, transformers and high-capacity resistors etc.
• Avoid direct sunlight
2Forced Ventilation (forced ventilation by use of a fan directly
mounted at Top of Panel)
3Controlled Circulation (controlled circulation by means of a fan in
the airtight enclosure panel)
4Full Room Cooling
(Use a cooler to cool the entire room in which the panel is installed)
(Notes)
Environmental conditions and cooling system should be as follows.
• Panel installed in room with low dust → 1 or 2
• Panel installed in room with dust → 3 or 4
When using a fan
• Attach an air filter to the suction mouth to prevent the entry of dust
• Periodically wash the air filter in water.
• Temperature sensors should be attached near the PLC to emit an
alarm in the event that the fan or air conditioner break down
etc.
● Low Temperature
In cold areas where the morning temperature falls below 0°C at the
time of start-up, attach a small space heater inside the panel to heat
the internal temperature to about 5°C. In order for the PLC power
supply to generate heat, don't turn off the power.
PLC
PLC
1Natural Cooling
Fan
PLC
PLC
Air Filter
2Controlled Ventilation 4Room Cooling System
Fan
3Controlled Circulation
PLC
PLC
Control Panel
Figure 1. Cooling Board
Cooler
1
■Humidity
In order to maintain the insulating properties of the PLC, relative humidity should be kept
within the range of 35% to 85%. In particular in the winter, when heaters are turned on and
off, sudden changes in temperature may be experienced resulting in condensation which can
lead to shorts or malfunctions. Where there is danger of such a change in temperature, power
should be kept on during the night and condensation should be prevented through such
measures as installing a small heater inside the panel to maintain low heat.
(See Figure 2)
Control Panel
Absorbent Material
PLC
Turn on
Powe r
Heater
Figure 2. Examples of Measures against Condensation
■Vibrations/Shocks
The PLC is tested in accordance with the environmental (electricity and
electrons) the sine wave vibration test method (JIS C0040/IEC68-2-6)
and the shock test method (JIS C0041/IEC68-2-27), so that vibrations
and shocks in the general specifications will not cause malfunctions.
However, the system should not be installed in a place where it will be
subject to regular vibrations or shocks, especially to the PLC and the
panel.
The following methods may be used to reduce the effect of vibrations and shocks.
1
For vibrations and shocks that originate externally, the panel should be removed from the
source. Alternatively, the PLC and the panel should be protected with the use of rubber.
2
Isolate vibrations such as through the construction of the building, flooring etc.
3Regarding shocks experienced during magnetic contactor
operation in the panel, the source of the shock or the PLC should
be protected by rubber so that the shock is not felt.
■Atmosphere
When using the system in any of the following kind of places, connections
may be loosened or elements and parts may experience corrosion, and an air
purge should be implemented to avoid this.
1Places where dust, salt, particles, soot or organic solvents etc are
common, and where the enclosure is sealed in such a way that the
internal temperature does not increase very much.
2Where corrosive gases are common, an air purge (air purification)
of the panel should be performed, to pressurize the panel and
prevent the intrusion of air from outside.
3
Places with flammable gases may be a cause of ignition. The system
should not be used without a fire prevention mechanism in place.
■Work Space
When installing the PLC and the panel, please consider their use, operability and
maintenance, and pay particular attention to the following.
1Make sure that there is sufficient space to operate programs and to
replace the unit. Further, for the sake of saftey and maintenance,
installation should be as far as possible from high pressure or high
power devices.
2Mount the PLC and I/O unit in a position in which the use of the
debugging tool and the connection and operation of peripheral
devices will be possible.
3
The PLC and I/O unit generally has a maintenance light, and this
should be easy for the operator to see, and in a position where it can
easily be reached.
4For systems using the PLC as a control system, it is likely that there
will be future additions and alterations to the system, so approx. 1020% extra space should be allowed for this.
5Where necessary, about 600 mm of space should be kept behind
the panel for the purpose of performing maintenance.
PLC Control Panel Electrical Conditions
The power supply, grounding, and noise make up the main elements of the electrical conditions. In the installation and wiring of the device, great care must
be taken to ensure that there is no danger to the human body, and that electrical signals are not obstructed (noise).
■PLC Installation Site
For the sake of safety in maintenance and operation, installation
should not be near high current (more than 600V) or high power
devices. Where this cannot be avoided, installation should be as far
away from such devices as possible.
(Example of Recommended Equipment Arrangement)
PLC
Control Panel Control Panel Panel with power line
(Example of Poor Equipment Arrangement)
Control Panel Control Panel Panel with power line
(See Figure 3)
PLC
● Arrangement of PLC and Each Unit (See Figure 4)
1The CPU and other adjoining units should be special or input units
where noise generation is limited.
2The coils and contacts in electromagnetic contactors and relays in
an external circuit are sources of noise. Locate them at least 100
mm away from the PLC.
Communications Unit
Power Unit
CPU
DC
I/O
Device
DC Unit
Te rm i n al Block
DC Unit
AC
I/O
Device
AC Unit
AC Unit
Figure 3. Ex amples of Equipment Arrangement
in Panel with High-voltage Device
Figure 4. Example of built-in type
2
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