The PLC technology that the 5G PLC IoT gateway relies on can be divided into stages such as input sampling, program execution, and output refresh.
3 working stages:
1. Input sampling stage
At this stage, the 5G PLC IoT gateway can read the input signals at the input terminals and store each input state in the corresponding input image register. At this time, the input image register is turned off. During program execution and output updates, the input image store is isolated from the external environment. It retains its contents until updated by the input signal being read again during the input scan of the next scan cycle.
The 5G IoT gateway does not directly use the on-site data when running the program and processing data but uses the image data input during the current sampling instead. Generally speaking, the length of the input signal should be greater than one scan, otherwise, the signal will be lost.
2. Program execution phase
When the IoT gateway is running the user program, according to the principle of “ladder diagram”, from left to right, from top to bottom. However, when the program jumps, it decides which step to jump to based on the jump situation. When the program is running, the PLC “reads” the corresponding input state from the input mirror register and “reads” the current state of the corresponding unit (“soft relay”) from the output mirror register when it is related to the instruction. Then execute the corresponding operation, and store the operation result in the output image register. For an output mirror register, the state of each unit (“soft relay”) is different during the operation of the program.
3. Output refresh phase
During the running of the program, the calculation result is not input to the output image area. In the output refresh phase, the 5G IoT gateway inputs the output variable in the output mapping area to the output latch and then generates the control output of the cycle through the output module. When the internal output relay is in the state of “1”, the output relay contactor will be closed, and the external load will be driven through the output terminal. All output devices maintain a scan cycle.
5G PLC IoT gateway working method
The working principle of the PLC IoT gateway is basically the same as that of the computer. However, the working method is different. The computer uses the working method of waiting for commands, while the 5G PLC gateway adopts the working method of cyclic scanning.
The working mode of cyclic scanning is a major feature of PLC technology. It can also be said that PLC works in “serial”, which is essentially different from the “parallel” work of traditional relay control systems. The serial working mode of PLC avoids the relay Problems of contact contention and timing mismatch in control systems.