The relationship between single chip microcomputer and PLC

AVR microcontroller is an enhanced RISC (Reduced Instruction Set CPU) high-speed 8-bit microcontroller with built-in Flash developed by ATMEL in 1997. AVR microcontrollers can be widely used in various fields such as computer peripherals, industrial real-time control, instrumentation, communication equipment, and household appliances.

The main features of AVR

High reliability, strong functions, high speed, low power consumption, and low price have always been important indicators for measuring the performance of microcontrollers, and are also necessary conditions for microcontrollers to occupy the market and survive.

Early microcontrollers were mainly due to low process and design levels, high power consumption, and poor anti-interference performance, so a safe solution was adopted: that is, a higher frequency division coefficient was used to divide the clock, resulting in a long instruction cycle and slow execution speed. Although later CMOS microcontrollers adopted measures such as increasing the clock frequency and reducing the frequency division coefficient, this situation has not been completely changed (51 and 51 compatible). Although some reduced instruction set microcontrollers (RISC) have been introduced, the practice of clock division is still followed.

The introduction of AVR microcontrollers completely broke this old design pattern, abolished the machine cycle, and abandoned the practice of complex instruction computers (CISC) pursuing complete instructions; it adopted a reduced instruction set, using words as the unit of instruction length, arranging rich operands and operation codes in one word (most of the single-cycle instructions in the instruction set are like this), with a short instruction fetch cycle, and can pre-fetch instructions to achieve pipeline operations, so it can execute instructions at high speed. Of course, this speed increase is backed by high reliability.

The hardware structure of AVR microcontrollers adopts a compromise strategy between 8-bit machines and 16-bit machines, that is, a local register storage stack (32 register files) and a single high-speed input/output solution (i.e., input capture registers, output comparison matching registers and corresponding control logic). It improves the instruction execution speed (1Mips/MHz), overcomes the bottleneck phenomenon, and enhances the function; at the same time, it reduces the overhead of peripheral management, relatively simplifies the hardware structure, and reduces the cost. Therefore, AVR microcontrollers have achieved an optimized balance in many aspects of software/hardware overhead, speed, performance and cost, and are cost-effective microcontrollers.

The AVR microcontroller has built-in high-quality Flash program memory, which is easy to erase and write, supports ISP and IAP, and is convenient for product debugging, development, production, and updating. The built-in long-life EEProm can store key data for a long time to avoid power loss. The large-capacity RAM on the chip can not only meet the use of general occasions, but also more effectively support the use of high-level languages ​​to develop system programs, and can expand external RAM like the MCS-51 microcontroller.

The I/O lines of the AVR microcontroller all have settable pull-up resistors, can be set as input/output individually, can be set (initial) high-impedance input, and have strong driving capabilities (power drive devices can be omitted), making the I/O port resources flexible, powerful, and fully utilized.

The AVR microcontroller has a variety of independent clock dividers on the chip, which are used for URAT, I2C, and SPI respectively. Among them, the pre-divider with up to 10 bits in conjunction with the 8/16-bit timer can provide a variety of timing times by setting the division coefficient through software. The unique design method of AVR microcontroller, "using timer/counter (single) bidirectional counting to form a triangular wave, and then coordinating with the output comparison matching register to generate a square wave with variable duty cycle, variable frequency, and variable phase (i.e. pulse width modulation output PWM)", is even more refreshing. The

enhanced high-speed synchronous/asynchronous serial port has the functions of hardware generation of checksum, hardware detection and check error detection, two-level receiving buffer, automatic baud rate adjustment positioning (when receiving), shielding data frame, etc., which improves the reliability of communication, facilitates program writing, and is more convenient for forming distributed networks and realizing complex applications of multi-machine communication systems. The serial port function greatly exceeds the serial port of MCS-51/96 microcontrollers. In addition, the AVR microcontroller is high-speed and the interrupt service time is short, so high baud rate communication can be realized.

Byte-oriented high-speed hardware serial interface TWI and SPI. TWI is compatible with I2C interface, and has the functions of hardware sending and recognition of ACK signal, address recognition, bus arbitration, etc., which can realize multi-machine communication of all 4 combinations of master/slave receiving/transmitting. SPI supports multi-machine communication of 4 combinations such as master/slave.

AVR microcontrollers have automatic power-on reset circuit, independent watchdog circuit, low voltage detection circuit BOD, multiple reset sources (automatic power-on and power-off reset, external reset, watchdog reset, BOD reset), and program delay after startup that can be set, which enhances the reliability of embedded systems.

AVR microcontrollers have multiple power-saving sleep modes, and can operate in a wide voltage range (5-2.7V), with strong anti-interference ability, which can reduce the software anti-interference design workload and hardware usage in general 8-bit machines.

AVR microcontroller technology embodies the integration of multiple devices (including FLASH program memory, watchdog, EEPROM, synchronous/asynchronous serial port, TWI, SPI, A/D analog-to-digital converter, timer/counter, etc.) and multiple functions (reset system to enhance reliability, sleep mode to reduce power consumption and anti-interference, interrupt system with a wide variety of categories, timer/counter with diversified functions such as input capture and compare match output, I/O port with replacement function...), which fully reflects the development direction of microcontroller technology from "self-operating" to "system on chip SoC".

PLC, or Programmable Logic Controller,

refers to a new type of industrial control device based on computer technology. In the draft PLC standard issued by the International Electrotechnical Commission in 1987, PLC was defined as follows:

"PLC is an electronic device for digital operation designed specifically for use in industrial environments. It uses a programmable memory to store instructions for performing logical operations, sequential operations, timing, counting and arithmetic operations, and can control various types of machinery or production processes through digital or analog input and output. PLC and its related peripherals should be designed to be easy to form an integral part of the industrial control system and easy to expand its functions."

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Characteristics of PLC

2.1 High reliability and strong anti-interference ability

High reliability is the key performance of electrical control equipment. PLC uses modern large-scale integrated circuit technology, strict production process, and advanced anti-interference technology in the internal circuit, so it has high reliability. For example, the F series PLC produced by Mitsubishi has an average failure-free time of up to 300,000 hours. Some PLCs using redundant CPUs have a longer average failure-free working time. From the perspective of the PLC's external circuit, the use of PLC to form a control system has reduced the number of electrical wiring and switch contacts to hundreds or even thousands of times compared to the relay contactor system of the same size, and the failure rate is greatly reduced. In addition, PLC has a hardware fault self-detection function, which can promptly issue an alarm message when a fault occurs. In the application software, the user can also program the fault self-diagnosis program of the peripheral device, so that the circuits and equipment in the system other than the PLC can also obtain fault self-diagnosis protection. In this way, it is not surprising that the entire system has extremely high reliability.

2.2 Complete supporting facilities, perfect functions, and strong applicability

. PLC has developed to today and has formed a series of products of various sizes, large, medium and small. It can be used in industrial control occasions of various sizes. In addition to the logic processing function, most modern PLCs have perfect data computing capabilities and can be used in various digital control fields. In recent years, a large number of PLC functional units have emerged, allowing PLC to penetrate into various industrial controls such as position control, temperature control, and CNC. Coupled with the enhancement of PLC communication capabilities and the development of human-machine interface technology, it has become very easy to use PLC to form various control systems.

2.3 Easy to learn and use, deeply welcomed by engineering and technical personnel

As a general industrial control computer, PLC is an industrial control equipment for industrial and mining enterprises. It has easy interface and its programming language is easy for engineers to accept. The graphic symbols and expressions of ladder diagram language are quite similar to relay circuit diagrams. Only a small number of switch logic control instructions of PLC can easily realize the functions of relay circuits. It opens the door for people who are not familiar with electronic circuits, computer principles and assembly language to use computers for industrial control.

2.4 Small workload for system design and construction, convenient maintenance and easy transformation

PLC uses storage logic instead of wiring logic, which greatly reduces the wiring outside the control equipment, greatly shortens the design and construction cycle of the control system, and makes maintenance easier. More importantly, it makes it possible to change the production process of the same equipment by changing the program. This is very suitable for multi-variety and small batch production occasions.

2.5 Small size, light weight and low energy consumption

Taking ultra-small PLC as an example, the bottom size of the recently produced varieties is less than 100mm, the weight is less than 150g, and the power consumption is only a few watts. Due to its small size, it is easy to install inside the machine, and it is an ideal control device for realizing mechatronics.

3. Application fields of PLC

At present, PLC has been widely used in various industries at home and abroad, such as steel, petroleum, chemical industry, electric power, building materials, machinery manufacturing, automobile, textile, transportation, environmental protection and culture and entertainment. The usage can be roughly summarized into the following categories.

3.1 Logic control of switch quantity

This is the most basic and most widely used application field of PLC. It replaces the traditional relay circuit to realize logic control and sequence control. It can be used for the control of single equipment, as well as for multi-machine group control and automated assembly line. Such as injection molding machine, printing machine, bookbinding machine, modular machine tool, grinder, packaging production line, electroplating assembly line, etc.

3.2 Analog quantity control

In the industrial production process, there are many continuously changing quantities, such as temperature, pressure, flow, liquid level and speed, which are analog quantities. In order for the programmable controller to process analog quantities, it is necessary to realize A/D conversion and D/A conversion between analog quantity (Analog) and digital quantity (Digital). PLC manufacturers all produce matching A/D and D/A conversion modules to enable programmable controllers to be used for analog quantity control.

3.3 Motion Control

PLC can be used to control circular motion or linear motion. In terms of control mechanism configuration, the switch quantity I/O module was directly used to connect the position sensor and the actuator in the early days, but now a dedicated motion control module is generally used. For example, a single-axis or multi-axis position control module that can drive a stepper motor or a servo motor. Almost all products of major PLC manufacturers in the world have motion control functions and are widely used in various machinery, machine tools, robots, elevators and other occasions.

3.4 Process Control

Process control refers to the closed-loop control of analog quantities such as temperature, pressure, and flow. As an industrial control computer, PLC can compile a variety of control algorithm programs to complete closed-loop control. PID adjustment is a commonly used adjustment method in general closed-loop control systems. Large and medium-sized PLCs have PID modules, and many small PLCs currently also have this function module. PID processing generally runs a dedicated PID subroutine. Process control is widely used in metallurgy, chemical industry, heat treatment, boiler control and other occasions.

3.5 Data Processing

Modern PLCs have functions such as mathematical operations (including matrix operations, function operations, and logical operations), data transmission, data conversion, sorting, table lookup, and bit operations, and can complete data collection, analysis, and processing. These data can be compared with reference values ​​stored in the memory to complete certain control operations, or they can be transmitted to other intelligent devices using communication functions, or printed and tabulated. Data processing is generally used in large control systems, such as unmanned flexible manufacturing systems; it can also be used in process control systems, such as some large control systems in the papermaking, metallurgy, and food industries.

3.6 Communication and networking

PLC communication includes communication between PLCs and between PLCs and other intelligent devices. With the development of computer control, factory automation networks have developed rapidly. All PLC manufacturers attach great importance to the communication function of PLCs and have launched their own network systems. Newly produced PLCs all have communication interfaces, and communication is very convenient.

4. PLC domestic and international status

The world's recognized first PLC was developed by the American Digital Equipment Corporation (DEC) in 1969. Limited by the conditions of components and the level of computer development at that time, the early PLC was mainly composed of discrete components and small and medium-scale integrated circuits, which could complete simple logic control and timing and counting functions. Microprocessors appeared in the early 1970s. People quickly introduced it into programmable controllers, which added functions such as calculation, data transmission and processing to PLCs, completing industrial control devices with real computer characteristics. In order to facilitate the use of engineers and technicians familiar with relays and contactor systems, programmable controllers use ladder diagrams similar to relay circuit diagrams as the main programming language, and all computer storage elements participating in calculations and processing are named after relays. At this time, PLC is a product of the combination of microcomputer technology and conventional control concepts of relays.

In the mid-to-late 1970s, programmable controllers entered the practical development stage, and computer technology was fully introduced into programmable controllers, making their functions leap forward. Higher computing speed, ultra-small size, more reliable industrial anti-interference design, analog quantity calculation, PID function and extremely high cost performance have established its position in modern industry. In the early 1980s, programmable controllers have been widely used in advanced industrial countries. The characteristics of the development of programmable controllers during this period are large-scale, high-speed, high-performance and product series. Another feature of this stage is that the number of countries producing programmable controllers in the world is increasing, and the output is rising. This indicates that programmable controllers have entered a mature stage.

At the end of the 20th century, the development characteristics of programmable controllers were more adapted to the needs of modern industry. In terms of control scale, large and ultra-small computers were developed during this period; in terms of control capabilities, various special function units were born, which were used in various control occasions such as pressure, temperature, speed, displacement, etc.; in terms of product matching capabilities, various human-machine interface units and communication units were produced, making it easier to match industrial control equipment using programmable controllers. At present, the application of programmable controllers in machinery manufacturing, petrochemicals, metallurgy and steel, automobiles, light industry and other fields has made great progress. The

introduction, application, research and development, and production of programmable controllers in China began with the reform and opening up. Initially, programmable controllers were used in large quantities in imported equipment. Then, the application of PLCs was continuously expanded in the production equipment and products of various enterprises. At present, China can produce small and medium-sized programmable controllers by itself. The CF series produced by Shanghai Dongwu Electric Co., Ltd., the DKK and D series produced by Hangzhou Machine Tool Electric Factory, the S series produced by Dalian Combined Machine Tool Research Institute, the YZ series produced by Suzhou Electronic Computer Factory and many other products have reached a certain scale and have been applied in industrial products. In addition, Sino-foreign joint ventures such as Wuxi Huaguang Company and Shanghai Xiangdao Company are also relatively well-known PLC manufacturers in China. It can be expected that with the deepening of China's modernization process, PLC will have a broader application space in China.

5. Future Prospects of PLC

In the 21st century, PLC will have greater development. From a technical point of view, new achievements in computer technology will be more applied to the design and manufacture of programmable controllers, and there will be varieties with faster computing speed, larger storage capacity and stronger intelligence; from the perspective of product scale, it will further develop in the direction of ultra-small and ultra-large; from the perspective of product matching, the product variety will be richer and the specifications will be more complete, and the perfect human-machine interface and complete communication equipment will better meet the needs of various industrial control occasions; from the perspective of the market, the situation of each country producing multiple varieties of products will be broken with the intensification of international competition, and a few brands will monopolize the international market, and internationally common programming languages ​​will appear; from the perspective of network development, the networking of programmable controllers and other industrial control computers to form a large control system is the development direction of programmable controller technology. At present, a large number of programmable controllers have been applied in the computer distributed control system DCS (Distributed

Control

System). With the development of computer networks, programmable controllers, as an important part of automation control networks and international general networks, will play an increasingly important role in many fields in and outside of industry. [page]

1 Basic knowledge of PLC

1.1 Development history of PLC

In the industrial production process, a large number of switch quantities are sequentially controlled. It performs sequential actions according to logical conditions, controls interlocking protection actions according to logical relationships, and collects data of a large number of discrete quantities. Traditionally, these functions are realized through pneumatic or electrical control systems. In 1968, GM (General Motors) of the United States proposed the requirement to replace relay control devices. The following year, American Digital Corporation developed a control device based on integrated circuits and electronic technology, and for the first time used programming methods for electrical control. This is the first generation of programmable controllers, called Programmable

Controllers (PC).

After the development of personal computers (PC for short), for convenience and to reflect the functional characteristics of programmable controllers, programmable controllers were named Programmable

Logic Controllers (PLC).

From the 1980s to the mid-1990s, PLC developed fastest, with an annual growth rate of 30~40%. During this period, PLC's ability to process analog quantities, digital computing capabilities, human-machine interface capabilities and network capabilities have been greatly improved. PLC has gradually entered the field of process control and replaced the DCS system that dominates the field of process control in some applications.

PLC has the characteristics of strong versatility, easy use, wide adaptability, high reliability, strong anti-interference ability and simple programming. The position of PLC in industrial automation control, especially sequential control, is irreplaceable in the foreseeable future.

1.2 Composition of PLC

From a structural point of view, PLC is divided into fixed type and combined (modular) type. Fixed PLC includes CPU board, I/O board, display panel, memory block, power supply, etc. These elements are combined into an inseparable whole. Modular PLC includes CPU module, I/O module, memory, power supply module, base plate or rack, and these modules can be combined and configured according to certain rules.

1.3 CPU composition

The CPU is the core of the PLC and acts as a nerve center. Each PLC has at least one CPU. It receives and stores user programs and data according to the functions assigned by the PLC system program. It uses scanning to collect the status or data sent by the field input device and stores it in the specified register. At the same time, it diagnoses the working status of the power supply and the internal circuit of the PLC and the syntax errors in the programming process. After entering the operation, the instructions are read one by one from the user program memory. After analysis, the corresponding control signal is generated according to the task specified by the instruction to command the relevant control circuit.

The CPU is mainly composed of an arithmetic unit, a controller, a register, and a data, control and status bus that realizes the connection between them. The CPU unit also includes peripheral chips, bus interfaces and related circuits. The memory is mainly used to store programs and data and is an indispensable component of the PLC.

From the user's point of view, it is not necessary to analyze the internal circuit of the CPU in detail, but there should be sufficient understanding of the working mechanism of each part. The CPU controller controls the CPU operation, and it reads, interprets and executes instructions. But the working rhythm is controlled by the oscillation signal. The arithmetic unit is used to perform digital or logical operations and works under the command of the controller. Registers participate in operations and store intermediate results of operations. They also work under the command of the controller.

CPU speed and memory capacity are important parameters of PLC. They determine the working speed, IO quantity and software capacity of PLC, thus limiting the control scale.

1.4 I/O module

The interface between PLC and electrical circuit is completed through the input and output part (I/O). The I/O module integrates the I/O circuit of PLC. Its input register reflects the input signal status and the output point reflects the output latch status. The input module converts the electrical signal into a digital signal and enters the PLC system, while the output module does the opposite. I/O is divided into switch input (DI), switch output (DO), analog input (AI), analog output (AO) and other modules.

Commonly used I/O classifications are as follows:

Switch quantity: According to the voltage level, there are 220VAC, 110VAC, 24VDC, and according to the isolation method, there are relay isolation and transistor isolation.

Analog quantity: According to the signal type, there are current type (4-20mA, 0-20mA), voltage type (0-10V, 0-5V, -10-10V), etc. According to the accuracy, there are 12bit, 14bit, 16bit, etc.

In addition to the above-mentioned general IO, there are also special IO modules, such as thermal resistors, thermocouples, pulse modules, etc.

The module specifications and quantity are determined by the number of I/O points. The I/O modules can be more or less, but their maximum number is limited by the basic configuration capabilities that the CPU can manage, that is, the maximum number of baseboards or rack slots.

1.5 Power supply module

PLC power supply is used to provide working power for the integrated circuits of each PLC module. At the same time, some also provide 24V working power for the input circuit. The power input types are: AC power supply (220VAC or 110VAC), DC power supply (commonly used is 24VDC).

1.6 Baseboard or rack

Most modular PLCs use baseboards or racks, which are used to: electrically connect modules so that the CPU can access all modules on the baseboard; mechanically connect modules so that modules form a whole.

1.7 Other equipment in the PLC system

1.7.1

Programming equipment: The programmer is an indispensable device for PLC development and application, monitoring operation, inspection and maintenance. It is used for programming, making some settings for the system, and monitoring the working conditions of the PLC and the system controlled by the PLC, but it does not directly participate in the field control operation. Small programmer PLC generally has a handheld programmer. At present, the computer (running programming software) generally acts as the programmer. That is, the host computer of our system.

1.7.2 Human-machine interface: The simplest human-machine interface is the indicator light and button. At present, the integrated operator terminal with LCD screen (or touch screen) is more and more widely used, and the computer (running configuration software) acting as the human-machine interface is very popular.

1.8 Communication networking of PLC

Relying on advanced industrial network technology, production and management data can be collected and transmitted quickly and effectively. Therefore, the importance of network in automation system integration engineering is becoming more and more significant, and some people even put forward the view that "network is the controller".

PLC has the function of communication networking, which makes PLC and PLC

Information can be exchanged between PLCs, between PLCs and host computers and other intelligent devices to form a unified whole and realize decentralized centralized control. Most PLCs have RS-232 interfaces, and some have built-in interfaces that support their own communication protocols. PLC communication now mainly uses data communication through multi-point interface (MPI), PROFIBUS

or industrial Ethernet for networking.

2 Basic principles of PLC control system design

2.1 Satisfy the control requirements of the controlled object to the greatest extent possible.

2.2 Under the premise of meeting the control requirements, strive to make the control system simple, economical, easy to use and maintain.

2.3 Ensure that the control system is safe and reliable.

2.4 Considering the development of production and process improvement, appropriate margins should be left when selecting PLC capacity.

3 PLC software system and commonly used programming languages

​​3.1 PLC software system consists of two parts: system program and user program. System programs include monitoring programs, compilers, diagnostic programs, etc., which are mainly used to manage the entire machine, translate program language into machine language, and diagnose machine failures. System software is provided by PLC manufacturers and has been solidified in EPROM, and cannot be directly accessed or intervened. User program is an application program (i.e. logic control) compiled by the user in the programming language of PLC according to the requirements of field control, which is used to realize various controls. STEP7 is a standard software package for configuring and programming SIMATIC programmable logic controllers, i.e. user program. We use STEP7 to configure hardware and compile logic programs, as well as monitor the results of logic program execution online.

3.2 Programming language provided by PLC

3.2.1 Standard language Ladder diagram language is also the most commonly used language. It has the following characteristics

3.2.1.1 It is a graphic language, which uses the terms such as relay contacts, coils, series connection and some graphic symbols in traditional control diagrams. The left and right vertical lines are called left and right busbars.

3.2.1.2 The contacts (contacts) in the ladder diagram are only normally open and normally closed. The contacts can be switches connected to the PLC input points or contacts of the PLC internal relays or the status of internal registers, counters, etc. 3.2.1.3

The contacts in the ladder diagram can be connected in series or in parallel, but the coils can only be connected in parallel and not in series.

3.2.1.4 Internal relays, counters, registers, etc. cannot directly control external loads, but can only be used as intermediate results for internal use by the CPU.

3.2.1.5 PLC scans events in cycles and executes in sequence along the ladder diagram. The results in the same scan cycle are retained in the output state register, so the value of the output point can be used as a condition in the user program. 3.2.2

Statement list language, similar to assembly language.

3.2.3 Logic function diagram language, expressed in the same way as semiconductor logic block diagrams. Generally, an operation box represents a function with input on the left and output on the right. 4 Use of STEP7 program 4.1 Create a project structure. A project is like a folder. All data exists in a hierarchical structure and can be used at any time. After creating a project, all other tasks are performed under this project. 4.2 Configure a station. Configuring a station means specifying the programmable controller you want to use, such as S7300, S7400, etc. 4.3 Configure hardware. To configure hardware is to specify the templates to be used in your control scheme and the addresses to be used in the user program to access these templates in the configuration table. The addresses are generally generated automatically by the program without modification. The characteristics of the template can also be assigned with parameters. 4.4 Configure network and communication connections. The basis of communication is to pre-configure the network, that is, to create a subnet that meets your control scheme, set network characteristics, set network connection characteristics and any connection required by the networked station. The network address is also automatically generated by the program. If you have no experience in changing it, do not modify it. 4.5 Define symbols. You can define local or shared symbols in the symbol table. Use these more descriptive symbol names instead of absolute addresses in your user program. Symbol names are generally written in letters and do not exceed 8 bytes. It is best not to use very long Chinese characters for description, otherwise it will have a great impact on the execution of the program. 4.6 Create a program. Use the ladder diagram programming language to create a program that is connected to or unrelated to the template and store it. Creating a program is one of the important tasks of our control engineering. Generally, linear programming (based on a block, OB1), distributed programming (writing function blocks FB, OB1 organization call), and structured programming (writing general blocks) can be used. We most often use structured programming and distributed programming together, and rarely use linear programming. 4.7 Download the program to the programmable controller. After completing all configuration, parameter assignment and programming tasks, you can download the entire user program to the programmable controller. When downloading the program, the programmable controller must be in the working mode that allows downloading (STOP or RUN-P). The RUN-P mode means that the program will be downloaded one block at a time. If an old CPU program is rewritten, a conflict may occur, so the CPU is generally switched to STOP mode before downloading. 5 Use of WINCC program 5.1 Introduction. WINCC is an industrial technology neutral system that solves visualization and control tasks in production and process automation. It has powerful functions for controlling automation processes and is an operation monitoring system based on personal computers. It is easy to combine standard and user programs to establish a human-machine interface to accurately meet actual production requirements. WINCC has two versions: RC version (with configuration and development environment) and RT version (only runtime environment). We generally use the RC version. 5.2 Simple steps for using WINCC 5.2.1 Variable management. First, determine the communication method and install the driver. Then define internal and external variables. The maximum license of external variables is 64K bytes, which is limited by the WINCC software license you bought. There is no limit on internal variables. 5.2.2 Screen generation. Enter the graphic editor. The graphic editor is a vector-oriented drawing program used to create process screens. You can also use the numerous graphic objects contained in the object and style library to create complex process screens. You can add dynamics to a single graphic object through action programming. 5.2.3 Alarm record settings. Alarm records provide display and operation options to obtain and archive results. You can arbitrarily select message blocks, message levels, message types, message displays, and reports. In order to display messages during operation, you can use the alarm control in the object library contained in the graphic editor. 5.2.4 Variable records. Variable records are used to collect data from the runtime and prepare them for display and archiving. 5.2.5 Report configuration, report configuration is implemented through the report editor. It is an integrated report system for messages, operations, archive contents and current or archived data timers or event-controlled documents. The form of user reports can be freely selected. 5.2.6 Application of global scripts, global scripts are the general name for C language functions and actions. According to different types, scripts are used to configure actions for objects and are processed by the system's internal C language compiler. Global script actions are used in the operation of process execution. A trigger can start the execution of these actions. 5.2.7 User manager settings, the user manager is used to assign and control the user's individual configuration and operation system editor access rights. Every time a user is created, the access rights to the WINCC functions are set and independently assigned to this user. Up to 999 different authorizations can be assigned.







































5.2.8 Cross-tab index, the cross-tab index is used to find and display all usages of an object, such as tags, screens and functions, etc. Using the "link" function, you can change the tag name without causing configuration inconsistencies.