Issues with online modification of S7-300
Thread Content
For the S7-300 system, I want to reset an accumulated flow value, but there is no reset button on the WinCC screen! Does this need to be modified in the low-level program block? However, modifying the program cannot be done online; it must be modified first and then downloaded, which will cause the CPU to stop working! Is it like this, expert? ? Also, if I want to change the range of a certain analog value, do I also have to make the changes in the program and then download it? ? ? ?
If the person who programmed it at that time had thought of Zhou Xiang, there should have been a reset variable. Connect it to the CPU, set it to ONLINE, and set this reset BOOL value to 1. There should be a pulse after the reset variable; if not, you also need to set the reset BOOL value to 0.
It can be modified online; downloading the modified program will not cause it to stop working
Download only the modified FC, not all of them; this generally has no impact on production
For the S7-300 system, I want to reset an accumulated flow value, but there is no reset button on the WinCC screen! Does this need to be modified in the low-level program block? However, modifying the program cannot be done online; it must be modified first and then downloaded, which will cause the CPU to stop working! Is that the case? ? It’s not like that; it won’t stop. Find the appropriate cumulative program and carry out the corresponding operations. Also, if I want to change the range of a certain analog value, do I also have to make the changes in the program and then download it? ? ? ? Yes, just download the current function or functional block
Using the online monitoring variable feature, the cumulative value can be a DB block, an M variable, etc.; the variables can be modified directly online
If you modify a certain FC, FB, or DB and then download the program (note that only the block is downloaded), it will not cause the CPU to stop, unless in two situations: 1. The program modification is incorrect; for example, an addressing error occurs (the CPU cannot find the address of the variable specified in the program), and there is no fault OB in the PLC to prevent such program errors, in which case the PLC will enter stop mode. 2. If you download the entire station, i.e., the hardware configuration program, this will cause the CPU to restart (in the case of 400H redundant PLCs, the hardware configuration can be updated online)
In other words, downloading the program alone won’t cause the CPU to stop working, right?
In other words, only the underlying program was modified, with nothing else changed. Then downloading the program won’t cause the PLC to stop, right? Things like modifying the range also work the same way – after modifying the program and downloading it, the CPU won’t stop running, right? ? ? One more question: under what circumstances can the CPU come to a stop? In addition to modifying the hardware configuration!
Can the 300 one also be modified online? Is it necessary to download the program block after making the modifications? Downloading the program block won’t cause the CPU to stop working, right? I learned Siemens PLC on my own. Don’t be offended:P