1. The communication between Cx-Programmer V5.0 and PLC is unstable:
Computer and PLC connection: Computer USB port (the computer does not have RS232 serial port) â†â†’ [USB to RS232 cable USB plug ↠→ USB to RS232 cable (Computer has been installed driver, and the default COM4 port has been set to COM1) â†â†’USB to RS232 male of RS232 cable] â†â†’[[RS232 female of PC-PLC connection cable â†â†’Medium of PC-PLC connection cable â†â†’ RS232 male of PC-PLC connection cable Head ]] ↠→ PLC RS232 female.
The USB-to-RS232 cable is shown in the single brackets above, and the connection cable between the computer and the PLC is in the double brackets. The connection cables between the computer and the PLC are as follows: (1). The males (for connection to the PLC) 2, 3, and 9 are respectively short with the females 2, 3, and 5 (for connection to a computer or USB to RS232 cable). Then, this is the official connection method of Omron; (2). The 2-2, 3-3, and 5-5 of the male and female terminals are respectively short-circuited. This is the normal connection method of the RS232 cable. Later, it was proved by practice that the above two computer and PLC connection cables can be used. The first kind of cable communication is stable and reliable. For the second kind of cable, when the communication between the computer and the PLC through the VC application program is not effective, it is easy to drop the frame (you can see it with the serial debugging assistant), only when the computer and the PLC share the power (common ground) problem found. Therefore, use the first type of connection cable as much as possible.
There is time for the computer and PLC to communicate properly, but time does not work - shows "Modem has been selected, to continue code?" Fault (actually "code" should be ""), once the fault message, it will certainly The following fault message appears:
When communication is not possible, the author used cloned back to the normal operating system before, re-installed Cx-ProgrammerV5.0 programming software and other methods, but also normal communication, but once the disconnection may not be able to communicate. It has also been found on several occasions that some programs can communicate with PLCs, while others do not. Therefore, the author will be able to communicate with the PLC program to back up, and then all delete the program instructions, and finally copy the target program instructions (copy notes can be automatically copied over), so that the computer can actually communicate with the PLC It! But - the next time this program may not be able to communicate properly! depressed……
According to the communication error message "Modem has been selected, to continue the code?", the author found a solution: right-click "My Computer" on the desktop, and then click "Properties" - "Hardware" - "Device Manager" , double-click "modem", right-click the expanded modem model, and click "disable".
In addition, the correct connection method is as follows: In the computer is not turned on and (and) PLC is not powered (otherwise the hot plug communication port may cause damage to the communication port (although this is not a good chance, but you better not to take chance)) Connect the USB-to-RS232 cable, the connection cable between the computer and the PLC, and then connect the computer and the PLC through the Cx-Programmer.
Please note: The USB port is not free to plug in. The key is to ensure that the RS232 port in the device manager is COM1. This situation on the author's computer: Initially, the default RS232 port was changed from COM4 port to COM1 port, but the plugged-in USB port was corresponding to COM4 port of RS232 (COM1 and COM3 were in use), unable to connect the computer and PLC; Plug in the above USB port corresponding to RS1 COM1 port (COM2, COM4 is in use), you can connect the computer and PLC.
2.Cx-Programmer V5.0 and PLC communication interference:
If the Cx-Programmer is online, the computer and the PLC are connected and in communication, and each time the equipment is shut down (nearly 20 AC contactors are disconnected at the same time), the Cx-Programmer will have a communication error and the connection between the computer and PLC will be interrupted. Whenever it is turned on (nearly 20 AC contactors pull in simultaneously), no communication error occurs.
Solution: Reconnect the PLC. If you are a perfectionist, you can add an RC RC module to each contactor coil (about 60 oceans per RC module). There may be no communication error (but I haven't tried it yet.) .).
3. Computer and PLC connection cable test:
Because it is thought that the connection cable between the computer and the PLC (the first conventional connection cable) is 2-2 short, 3-3 short, and 5-5 short, so consider connecting the PC and the PLC directly with the USB ↠→ RS232 cable. Is it not possible to save a connection cable if this is possible? The following is the test result of directly connecting the computer and PLC with USB â†â†’RS232 cable:
The following error occurred during the first communication at the time: "The selected port was occupied by another application"; the following error occurred during the second communication:
Why does it not matter if the computer is connected to the PLC through the above two connection cables, but it is not possible to use the USB to RS232 cable directly to connect to the PLC? The following is the analysis process:
The first possibility: the reason for the impedance. Although the above two connecting cables are straight-wired, there is impedance, and more impedance can be connected normally. However, this reason seems to be far-fetched. Even the author himself cannot believe it.
The 2nd possibility: The USB to RS232 male connector is in poor contact with the PLC's female connector, and a cable can be connected to it. The USB to RS232 male connector is in good contact with the female connector of the cable. The head is in good contact with the PLC's female head. This guess comes from a computer failure that the author encountered: a computer's mouse can not be used, in addition to a normal mouse, the failure of the mouse to other computers can be used normally. Finally, it is suspected that the connection between the mouse connector and the motherboard socket is poor, and the mouse plug is broken and then coated with a layer of solder. The result is normal! But for the speculation that the USB-to-RS232 male connector is not in good contact with the PLC's female connector, I do not think it is possible because he cannot explain the fault that the selected port is occupied by another application.
Finally think of another possibility: USB to RS232 directly connected to the PLC is equivalent to USB to RS232 serial port and PLC serial port 1-1,2,2,3-3,4-4,5-5,6-6, 7-7, 8-8, 9-9 correspond to each other, and only two pairs of terminals 2-2, 3-3, and 5-5 are connected through the connection line. This shows that 1-1, 4-4, 7- 7,8-8,9-9 at least one pair can not be connected, otherwise there will be problems, and it may also damage the communications port of the PLC and the computer.
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