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S7-300 CPU 31x -- Product information -- Determining performance and quantity frameworks
How many connections and communication jobs do SIMATIC S7-300 and S7-400 support simultaneously?
Which connection resources are occupied in the S7-300 CPU for communication connections and services of the Industrial Ethernet CP?
What are the system limits in an F CPU for safe bidirectional data communication using S7 Communication?
How can you determine the size of the load memory and main memory of a SIMATIC S7-300/400 CPU?
What restrictions are there for active jobs when communicating with SFC 58 / SFC 59 and SFB 52 / SFB 53 via PROFIBUS DP and PROFINET IO?
Where do you find information on transmission times on the PROFIBUS or Industrial Ethernet?
What is a hardware interrupt and how do they work in the S7-300 system?
What is the maximum number of OPs that a CPU S7-300 can communicate with?
What can you do when the power requirement of the modules in the subrack exceeds the power supply provided by the CPU on the backplane bus?
Does PROFIBUS DP communication use connection resources?
What is the maximum number of CP modules that can be slotted in a SIMATIC S7-300/400 station?
Why, in the case of a networked SIMATIC S7, does the connection to the OP clear down when you call diagnostics functions with the PG or transfer blocks?
How many breakpoints can you insert when debugging a program?
Why, in the case of a networked SIMATIC S7, does the connection to the OP clear down when you call diagnostics functions with the PG or transfer blocks?
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Each connection requires connection resources for the end point or for the transition point (e.g. CP) on the stations concerned. The number of connection resources is CPU/CP-specific. The behavior described above indicates a resources bottleneck. You might not even be able to go online at all with your PG. Check the number of existing communication connections. Does you CPU have sufficient connection resources? The relevant information is available in the manuals...

  • Automation System S7-400 Module Specifications (Entry ID 1117740)
  • CPU 31xC and CPU 31x, Technical Data (Entry ID: 12996906)
  • SIMATIC PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP (Entry ID 8860591).

Communication problems with OPs due to lack of connection resources occurred in SIMATIC S7-300 usually with old CPUs, which on the one hand had little connection resources and on the other the connection resources could not yet be reserved for PG, OP and S7 Basic communication. A table of the CPUs with which you can reserve resources is included in Entry ID: 299124. Your problem might well be cleared by reserving. Otherwise you should upgrade to a new CPU firmware version.

 Entry ID:21909078   Date:2005-08-23 
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