01
Question: How can an S7-1200 PLC be implemented as an SNTP server for clock synchronization in the clock synchronization function?
Answer: The S7-1200 PLC can only function as an NTP client for clock synchronization. To realize the SNTP server functionality, you need to download and configure the corresponding library through a link.
02
Question: Why does the "permanent 1" signal not take effect in the program after configuring the system memory?
Answer: After configuring or modifying the system memory, it is crucial to ensure that the configuration is re-downloaded to the CPU; otherwise, the configuration will not be effective.
03
Question: In the "Startup" feature of CPU properties, what is the meaning of "Compare preset with actual configuration match" setting? What do "match" or "compatibility" refer to here?
Answer: Compatibility in matching refers to the requirement that the input and output counts, electrical and functional characteristics of the modules should match the current modules. Compatible modules can fully replace the configured modules, and the functional requirements must not be lower than those of the replaced modules.
For example, a 16-channel digital input module can replace an 8-channel digital input module, but not vice versa. Similarly, a 16-channel transistor digital output module cannot replace a 16-channel relay digital output module.
Under the setting of "Start CPU only if compatible," if the inserted modules are compatible with the configuration, the CPU will start normally; if not, the CPU will not start.
04
Question: Why is the CPU unable to start after being powered on?
Answer: If the CPU fails to start and enter the RUN mode after being powered on, you can follow these steps to troubleshoot:
(1) According to the settings in the hardware configuration as shown in Figure 1, confirm whether the "Startup" option is configured to "Warm Restart - RUN Mode". If not, you need to manually modify the configuration to "Warm Restart - RUN Mode", then recompile and download the hardware configuration.
If "Warm Restart - Previous Operating Mode" is selected, then if the CPU stopped due to a fault before being powered off, upon being powered on again, the CPU will retain its STOP mode status from before the power was lost.
If "No Restart" is selected, the CPU will directly enter STOP mode upon being powered on.
(2) If the CPU fails to start, you should check the CPU's diagnostic buffer online to identify the specific reason why the CPU cannot start. For example, the diagnostics may report an error such as "No data record available for central device option processing or invalid". At this point, you need to carefully review the fault information to further understand and resolve the issue.
(3) The CPU may also enter STOP mode due to the following faults:
Hardware modules on the central rack have failed.
Modules on the central rack have undergone hot-swapping.
The CPU power supply is unstable or subject to interference on the power supply line.
A memory card is inserted into the CPU.
The "Exceeded Maximum Cycle Time" occurs twice within the same program cycle without resetting the cycle timer.
05
Question: Why is there a 7-hour or 8-hour difference between the local time read by the CPU and the current actual time?
Answer: The current real-time is Beijing Time, while the default time zone in the CPU properties is set to UTC+01:00, and Daylight Saving Time (DST) may be activated by default. To obtain the correct local time, you need to set the time zone in the CPU properties to UTC+08:00, deactivate Daylight Saving Time, and then download the configuration to the CPU.
This will ensure that the time read by the CPU is Beijing Time. Only then can the local time be correctly read.
06
Question: Why is the "Allow PUT/GET access from remote partners (PLC, HMI, OPC, etc.)" option in the "Connection Mechanism" section of the "Protection/Safeguarding and Security" page in the CPU properties grayed out and unable to be selected?
Answer: If the "Allow PUT/GET access from remote partners (PLC, HMI, OPC, etc.)" option is grayed out and cannot be activated, it may be due to the CPU's protection level being set to the highest level, which is "No Access (Full Protection)". In this case, you need to set the protection level to another level in order to activate this option.