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Entry type: FAQ Entry ID: 22410800, Entry date: 10/19/2018

What do you have to do if, after adding a CP or an FM module, the SIMATIC S7-300 CPU no longer switches to RUN mode?

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After adding a CP or an FM module, the SIMATIC S7-300 CPU no longer switches to RUN mode but remains in STOP mode.

When adding a CP or an FM module you normally proceed as follows.

  1. You enlarge the SIMATIC S7-300 station physically with a CP or the FM module.
  2. In STEP 7 you change the hardware configuration to accommodate the new module.
  3. You load the changed system data into the CPU in STOP mode.
  4. You switch the CPU to RUN mode.

The S7-300 CPU remains in STOP mode. This behavior is signaled as follows:

  1. The "SF" LED lights red (sumcheck error).
  2. The following events are displayed in the diagnostics buffer:
    - Event ID 16# 49A0
    STOP because of parameter error or impermissible difference between setpoint and actual configuration: Startup inhibit
    - Event ID 16#5962
    Parameter error with start inhibition in party line/K bus parameters
    Error type: I/O bus not OK, which means that a module does not enter a type ID within the module monitoring time.
    - Event ID 16#6547
    Parameter error when parameterizing modules (not via P bus, but abort of download)

The K bus configuration is evaluated by the CPUs listed in Table 1 only at Power OFF/ON and Overall Reset. This evaluation is not made when the system data is simply loaded into the station. Configured modules that use the K bus therefore cannot be reached by the CPU. This can lead to the above-mentioned events in the diagnostics buffer.

Execute the following steps to analyze the cause of this parameterization error:

  1. Switch the power supply off and on again.
  2. Do an overall reset of the S7-300 CPU. The system data is loaded from the MMC (Micro Memory Card) into the RAM.
  3. Load the configuration offline, for example with a PG/PC, to the MMC (Micro Memory Card) and then use the MMC in your S7-300 CPU.
  4. Check whether the CP 343-1 is networked in the hardware configuration.
  5. Save the project with the option "With reorganization (slow)", erase the MMC (Micro Memory Card) of the S7-300 CPU and slot the erased MMC (Micro Memory Card) back in the S7-300 CPU and load the project into the S7-300 CPU.
  6. Export the hardware configuration and import the hardware configuration into a new STEP 7 project. Execute the following steps:
    - Compile the hardware configuration
    - Copy all the blocks of the user program into the new STEP 7 project.
    - Check the connections in NetPro. If necessary, add connections in NetPro.
  7. Check the IMs by replacing the IMs or slotting the CP into the individual IMs. See whether the behavior re-occurs. The event 16#6547 in the diagnostics buffer indicates that one of the IMs is defective. 

Table 1 shows an overview of the S7-300 CPUs that are affected by this behavior.

S7-300 CPUArticle numberFirmware version
Standard CPUs  
CPU 315-2 PN/DP6ES7315-2EG10-0AB0<  V2.3.4
CPU 317-2 DP6ES7317-2AJ10-0AB0< V2.1.10 
CPU 317-2 PN/DP6ES7317-2EJ10-0AB0< V2.3.4
Technology CPUs  
CPU 315T-2 DP6ES7315-6TG10-0AB0≤ V2.4.1
CPU 317T-2 DP6ES7315-6TJ10-0AB0≤ V2.4.1
Fail-safe CPUs  
CPU315F-2 PN/DP6ES7315-2FH10-0AB0 < V2.3.4
CPU 317F-2 DP6ES7317-6FF00-0AB0< V2.1.10 
CPU 317F-2 PN/DP6ES7317-2FJ10-0AB0 < V2.3.4

Table 1

The behavior occurs with all K-bus users, i.e. with the Ethernet and PROFIBUS CPs and function modules FM353, FM354, FM355 S/C and FM357(-2), for example.

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