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S7-300 CPU 31x -- Product information -- Background and system information
How many devices can you connect to an S7-300/S7-400 using the Modbus/TCP protocol?
Which IO controllers and IO devices support the following functions in STEP 7 (TIA Portal): IRT, prioritized startup, MRP, MRPD, PROFIenergy, Shared device, MSI/MSO, I device, Isochronous mode, System redundancy and Option handling?
What is the emergency address (emergency IP) of a CPU and when is this enabled or disabled?
All-round protection with Industrial Security - System Integrity
What are the differences between OPEN MODBUS / TCP Redundant V1 and OPEN MODBUS / TCP Redundant V2?
What is the difference between "normal routing" and data record routing?
Which SIMATIC S7-300/S7-400 modules support the NTP time-of-day message and how do you activate this kind of time synchronization?
Which manufacturer ID, in other words OUI (Organizationally Unique Identifier), does SIEMENS AG use for the MAC addresses of network-compatible devices?
What should you watch out for when using the alarm numbering procedure?
Which IO controllers and IO devices support the following functions in STEP 7 V5.5: IRT, prioritized startup, MRP, MRPD, PROFIenergy, Shared device, I device, sochronous mode, System redundancy and Option handling?
What is the maximum number of parameters that can be assigned to an FC and FB in the S7-300 CPU?
Which types of connection/protocols do the S7-300/400 CPUs and the CPs support by default?
Which PROFINET nodes support automatic commissioning (device replacement without interchangeable medium) in the case of topological configuration and device replacement without topological configuration?
Which PROFINET nodes support the extended PN diagnostics and what do you have to configure?
Why is only a warm start available for S7-300?
Which SIMATIC S7 modules support the "Direct Data Exchange" function (internode communication)?
Which entries deal with consistent data in conjunction with distributed I/O?
What properties, advantages and special features does the S7 Basis Communication offer?
What properties, advantages and special features does the global data communication offer?
What is the connection between subnet masks and IP addresses with regard to subnetting and supernetting (Classless Inter Domain Routing CIDR)?
Which modules support the S7 routing function?
How can you obtain an overview of the memory concept of SIMATIC S7-300 CPUs and C7 devices?
Retentivity behavior of S7-300 CPU 31x and complete devices C7-6xx with MMC
Status of the run-time meter after overall reset
Why does the retentivity behavior of the S7-300 CPUs and C7 devices without MMC (Micro Memory Card) influence the contents of the variables?
Local data addressing with S7-300 / S7 400
S7 300 run-time meter doesn't give any value
S7-400 CPU 41x -- Product information -- Background and system information
How many devices can you connect to an S7-300/S7-400 using the Modbus/TCP protocol?
When compiling a CFC chart, why is the error message "Time stamp conflict" displayed in connection with the Modbus/TCP FBs for S7-400 CPUs?
Which IO controllers and IO devices support the following functions in STEP 7 (TIA Portal): IRT, prioritized startup, MRP, MRPD, PROFIenergy, Shared device, MSI/MSO, I device, Isochronous mode, System redundancy and Option handling?
All-round protection with Industrial Security - System Integrity
What are the differences between OPEN MODBUS / TCP Redundant V1 and OPEN MODBUS / TCP Redundant V2?
What is the difference between "normal routing" and data record routing?
Which SIMATIC S7-300/S7-400 modules support the NTP time-of-day message and how do you activate this kind of time synchronization?
Which manufacturer ID, in other words OUI (Organizationally Unique Identifier), does SIEMENS AG use for the MAC addresses of network-compatible devices?
What should you watch out for when adding components or changing their parameters using CiR (Configuration in Run)?
Which IO controllers and IO devices support the following functions in STEP 7 V5.5: IRT, prioritized startup, MRP, MRPD, PROFIenergy, Shared device, I device, sochronous mode, System redundancy and Option handling?
Which types of connection/protocols do the S7-300/400 CPUs and the CPs support by default?
Which PROFINET nodes support automatic commissioning (device replacement without interchangeable medium) in the case of topological configuration and device replacement without topological configuration?
Behavior of the CPU after power off without back-up battery
I/O addressing with DP slaves
Which PROFINET nodes support the extended PN diagnostics and what do you have to configure?
What is the difference between a restart (warm restart), cold restart and hot restart of a S7-400 CPU?
Which SIMATIC S7 modules support the "Direct Data Exchange" function (internode communication)?
What properties, advantages and special features does the S7 Basis Communication offer?
What properties, advantages and special features does the global data communication offer?
Which entries deal with consistent data in conjunction with distributed I/O?
What is the connection between subnet masks and IP addresses with regard to subnetting and supernetting (Classless Inter Domain Routing CIDR)?
Which modules support the S7 routing function?
CPU does not work in RUN
What does "Correction factor" mean in the "Diagnostics/Clock" tab of the CPU's Properties dialog?
What is multicomputing mode and what are the differences to operating in the segmented subrack?
Differing information on the requirement of offline/ online memory
How can I get an overview of the S7-400 memory concept?
What properties, advantages and special features does the S7 Basis Communication offer?
Part number:

Description:
S7 Basis Communication involves unconfigured communication connections via which data is transferred on the MPI bus or on the PROFIBUS. The communication connections used are dynamic, i.e. they are set up and released again by the application.

S7 Basis Communication is on Layer 7 ("Application Layer") of the ISO-OSI reference model:

Fig. 01: ISO-OSI reference model

S7 Basis Communication services:
 
Services Description
I_PUT / I_GET This unidirectional service permits you to fetch or write the data of an I slave connected to your own PROFIBUS DP master system.
X_PUT / X_GET This unidirectional service permits you to fetch or write the data of a module connected to the same MPI bus.
X_SEND / X_RCV This bidirectional service permits you to fetch or write the data of a module connected to the same MPI bus.

Properties of the services:
The data volume of the data to be transferred is a maximum of 76 bytes.
Service / Properties I_PUT / I_GET X_PUT / X_GET X_SEND / X_RCV
Max. user data length 84 bytes / 94 bytes 76 bytes 76 bytes
Communication concept Client / Server Client / Server Client / Client
Connection resources1) 0-12 (S7-300)
16-64 (S7-400)
- see CPU specification
0-12 (S7-300)
16-64 (S7-400)
- see CPU specification
0-12 (S7-300)
16-64 (S7-400)
- see CPU specification
Possible address areas E, A, M, D E, A, M, D E, A, M, D
Blocks SFC 72 "I_GET" / SFC 73 "I_GET" SFC 67 "X_GET" / SFC 68 "X_PUT" SFC 65 "X_SEND" / SFC 66 "X_RCV"

1) The connections resources to be reserved for the S7 Basis Communication are set in the STEP 7 Hardware Configuration in the Properties dialog of the configured CPU -> "Communication" tab.

Advantages of S7 Basis Communication with the service

  • There is no need to configure communication connections.
  • Data can be transferred dynamically and variably.
  • Data is sent and received consistently.
  • The connection resources can be controlled by the S7 program in the CPU.
  • The Client / Server and Client / Client communication concepts are possible.

Disadvantages of S7 Basis Communication with the service

  • S7 Basis Communication can be used only in homogeneous SIMATIC structures.
  • Only small volumes of data can be transferred.

Notes:

  • You can find general information about communication via SIMATIC S7 in Entry ID 20982954.
  • There is information available on the SFCs for S7 Basis Communication is available in the manual "System Software for S7-300/400 System and Standard Functions" in Entry ID: 1214574.

 Entry ID:28866132   Date:2008-04-01 
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