SIMATIC TIA博途6AV2101-4AB03-0AE5
本司专业经营西门子PLC
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上海西皇电气设备有限公司
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An overview of the working principle of PLC
Note: the PLC is a miniature computer in nature, its working principle and common computer has many characteristics similar to the computer, but the work is quite different with the computer, has a certain particularity. The early PLC is mainly used to replace the traditional relay control device composed of a contactor, but the operation of the two different ways. The relay control device adopts the method of parallel operation of hard logic
PLC is a microcomputer in nature, it is similar to the general computer, and it has many characteristics of the microcomputer, but its working mode is different from that of the microcomputer.
The early PLC is mainly used to replace the traditional relay control device composed of a contactor, but the operation of the two different ways. Relay control device adopts hard logic parallel operation mode, if the coil of a relay is switched on or off, all the relay contact (normally open and normally closed contacts) in any position control circuit, will immediately act at the same time. The PLC is an order one by one scanning operation mode of the user program, i.e. if a coil is switched on or off, all contact with the coil will not immediately move to the contact must be scanned before action. In order to eliminate the two because of this difference caused by different modes of operation, taking into account the relay contact time of various control devices in general in more than 100ms, and the PLC scan the user program time is less than 100ms, PLC uses a different from the general microcomputer operation mode - cycle scanning.
General use of computer, waiting for input response processing of the work, no input has been waiting for input, such as a keyboard or mouse I/O trigger signal, is processed by the computer's operating system, into the corresponding program. Once the program is executed, wait for the state to wait for input. The PLC I/O operation, data processing, etc., using a circular scanning mode of operation. |
