Siemens PLC common faults - solutions - Huaqiang Electronic Network

Filter 18.432M

Question: Which settings are retained after a full CPU reset?

Solution: The memory is not completely deleted when the CPU is reset. The entire main memory is completely deleted, but the data loaded in the memory and the data stored on the Flash-EPROM memory card (MC) or micro memory card (MMC) are all retained. In addition to loading memory, timers (except CPU 312 IFM) and diagnostic buffers are also reserved. A CPU with an MPI interface or a combined MPI/DP interface retains the current address and baud rate used by the interface only before all resets. On the other hand, another PROFIBUS address is also completely deleted and can no longer be accessed. The protection level set before all resets is also retained.

Q: Is the MPI and PROFIBUS interface settings retained after updating the operating system of the CPU 41x?

ANSWER: If you have updated a CPU operating system, you must reload the program because the CPU has made a full reset. A CPU with an MPI interface or a combined MPI/DP interface retains the current address and baud rate used by the interface only before the operating system is updated. On the other hand, another PROFIBUS address is completely deleted and cannot be accessed anymore. Important: After resetting the PG/PC, communication with the CPU can only be established via the MPI or MPI/DP interface. Note: The protection level set before the operating system update is the same as the MPI address. The details of how to update an operating system in the provided download are available for the operating system of various CPUs.

Question: How do you change the response monitoring time in a PROFIBUS DP network?

ANSWER: If the bus profile is set to "user-defined", the response monitoring time can only be changed manually. Otherwise, the corresponding domain is grayed out and cannot be changed. /p The following is a description of the relevant dialog: Select a bus component and double click. In the registry "General", click the button "PROFIBUS" and go to "Parameter". Click on "Properties". The bus profile can be changed in "Network settings". If you click "Bus parameter", the response monitoring time will be displayed. /li This time can be calculated automatically. To do this, click on the button "Recalculate" or enter a value between 15.000 and 975.000.000 t_bit. The response monitoring time is valid for the entire PROFIBUS DP network.

QUESTION: Which information is stored in the diagnostic buffer of the SIMATIC S7-CPU?

ANSWER: System diagnostics are used to identify, evaluate and display errors that occur in automated systems. To this end, in each of the CPs and modules with system diagnostic capabilities, there is a diagnostic buffer that contains detailed information on all diagnostic results. The error is identified by the operating system of the module as a unique number (cause) within the entire system, including the location and time at which the error occurred and displayed in plain text. The error history is also logged because the error message is automatically stored in the diagnostic buffer without user assistance. The basic functions of system diagnostics include all error events of the operating system and some of the program sequences of the user program, which are stored in the diagnostic buffer with time, error number and additional relevant information. In addition, the user can enter user-defined diagnostic events (such as information about the user program) in the diagnostic buffer or send user-defined diagnostic results to the connected stations (monitoring devices such as PG, OP, TD). Diagnostic Buffer Diagnostic Buffers identify fault sources faster, thereby increasing system availability. Evaluate the last event before STOP and look for the cause of the STOP. The diagnostic buffer is a circular buffer with a single diagnostic entry that is displayed in the sequence of events; the first entry shows the most recent event. If the buffer is full, the earliest event of g will be overwritten by the new entry. Depending on the CPU, the size of the diagnostic buffer is fixed or fixed, or it can be set via parameters in HW Config. The entries in the /p diagnostics buffer include: Fault event operating mode transitions and other user-defined diagnostic events that are important to the user. (SFC52 WR_USMSG) In operating mode STOP, there are as few stored events as possible in the diagnostic buffer. So that the user can easily find the cause of the STOP in the buffer. Therefore, entries are stored in the diagnostic buffer only when the event requires the user to generate a response (such as scheduling a system memory reset, the battery needs to be recharged) or when important information (such as firmware update, station failure) must be registered. /p The user program is not processed in the operating mode STOP. Therefore, there are no diagnostic buffer entries that are triggered by the user program. The entries in the diagnostic buffer do not include: Temporary error statistics or traces of information about data or quality of service. Cyclic OB start-up loops occur in the event of a fault that is usually only entered the first time, after which only when the error is caused The reason is recognized before it is entered. This ensures that the overflow does not overwrite important entries. With online help, users can analyze diagnostic buffer entries and find possible causes and remedies for incidents. Reasonable evaluation of diagnostic buffers Reasonable evaluation of diagnostic buffers is generally done by diagnostic tools such as S7 system diagnostics. The user program can be read from the diagnostic buffer, however, it cannot be used to reduce the controller's reaction to the user program.

Question: Why does it not change the date from 29.02 to 01.03 correctly after shutting down CPU 945 on February 29th?

ANSWER: If a correction factor that is not equal to 0 is set for the hardware clock of the CPU 945 (current firmware version is Z03), and the CPU is in the power-off state when the date changes, then the date will not change from 29.02 to 01.03 in the following year. Execute correctly. Example: Set the date to 29.02. The setup time is 23:59:00. Now turn off the CPU and wait until the date has changed. When reopened, the date on the CPU is still 23:52:50 of 29.02. A setting in which the correction factor is not equal to zero results in an incorrect time correction value being calculated at the following month. Then, the hardware clock is also set to the error time and date. /p Remedy: If a correction factor equal to zero is used, the time drift behavior no longer occurs. You can set the correction factor yourself.

Question: Which drives support the new function "Clock Synchronization" of SIMATIC?

ANSWER: Starting with firmware version V3.1, the CPU of the SIMATIC S7-400 series supports the new TIA system function "Clock Synchronization". Clock synchronization is a direct link between the I/O module and the user program in the isometric DP cycle. The clock synchronization function is supported by the complete product groups "SIMODRIVE" and "MASTERDRIVE MC". The requirements for configuring the drive are from Drive ES Basic above V5.2, STEP 7 V5.2 and firmware version V3.1 for S7 400 CPU. Please note here that only the internal DP interface of the CPU is available for communication.

Question: What is entered in the image when there are differences on the redundant digital input modules?

ANSWER: In PII (input process image), the last average of the redundant digital input modules is valid until it is mislocated. In the event of a discrepancy, the module identified by the CPU as faulty is in a passivated state (the CPU no longer reads in the relevant input bytes). In this case, the value of the module in the non-passivated state is valid. After this, the error can no longer be recognized because the signal on the non-passivated module is always accepted by the CPU with the correct signal. Ensuring that the localization of the faulty digital input module is only possible through the IO type (interconnect) and FLF (fault localization tool).

Question: Why do I need to use a SIFI-C filter in some peripheral modules? How are these modules connected?

Solution: For several peripheral modules, a SIFI C filter must be used as it is used in CE certification to meet HF absorption and emissions requirements. Information about which filter to use on the module can be found in the current catalog or in the current system manual. For digital output modules, the filter must be switched to the load voltage source and for the digital input module it must be switched to the module/sensor supply. For analog modules, the filter must be switched to the module power supply. The same filter can be used for a set of input and output modules.