Simple programmers can only program

Simple programmers can only program online, not directly enter and edit ladder programs. It needs to convert the ladder program into the instruction list program for input. Simple programmers are small and cheap. It can be directly inserted into the programming interface of the PLC, and can also be connected to the PLC through a dedicated cable, which is convenient for programming and debugging. Some simple programmers have a storage box that can be used to store user programs, such as Mitsubishi's fx-20p-e simple programmer.Intelligent programmers are also called graphics programmers. It is essentially a special portable computer, such as the Mitsubishi gp-80fx-e intelligent programmer. It can be programmed online and offline. It can directly input and edit the ladder program, which is more intuitive and convenient to use, but the price is relatively high and the operation is relatively complicated. Most smart programmers have a disk drive, which provides a recorder interface and a printer interface.The user program is determined by the PLC's control object, and the application program is compiled by the user according to the object's production process control requirements. In order to facilitate reading, inspection and modification, user programs are usually stored in CMOS static RAM, and use lithium batteries as backup power to ensure that no information will be lost when the power is turned off. In order to prevent interference from destroying the program in RAM, when the user program runs normally and does not need to be modified, it can be solidified in the EPROM. Many plc now use EEPROM directly as user memory.Work data is data that is frequently changed and accessed during PLC operation. It is stored in RAM to meet random access requirements. In the working data memory of the PLC, there is a storage area for storing input and output relays, auxiliary relays, timers, counters and other logical devices. The status of these devices is determined by the initial settings and operation of the user program. As needed, some data is maintained in the current state by the backup battery when the power is turned off. The storage area where data can be saved when power is turned off is called the hold data area.Since the system program and work data are not directly related to the user, the form and capacity of the memory listed in the PLC product catalog or user manual refer to the user program memory. When the user memory capacity provided by the PLC is insufficient, many PLCs also provide memory expansion functions.I / O unit, also known as I / O unit or I / O module, is the connecting part between PLC and industrial production site. The PLC can detect various data of the controlled object through the input interface, and use these data as the basis for the PLC to control the controlled object; meanwhile, the PLC sends the processing result to the controlled object through the output interface to achieve the control purpose.