Siemens SIMATIC S7 ISO on TCP
Siemens SIMATIC S7 ISO on TCP communication protocol
Supported device types and versions
This protocol supports data reading/writing from the control PLC machines Siemens SIMATIC:
types S7-300 and S7-400 equipped by an ethernet interface for the S7 ISO over TCP communication .
types S7-1200, S7-1500
Siemens LOGO
Siemens Microbox
Note: communication via Profinet/Profibus adapter ACCON-NetLink-PRO compact produced by company DELTALOGIC has been verified. Communication with multiple S-300 series PLCs on Profibus worked after the firmware upgrade of the adapter to version V2.54 (31. march 2015) with the adapter's BIOS version V2.39 (7. June 2011). When the adapter's firmware was version V2.37 (8. August 2011), communication could not be correctly established.
Note: communication with PLC Siemens LOGO was tested. A part of memory that is accessible for reading/writing is the V area which is seen as DB1.
Note: the protocol has a "big-endian" data representation.
Communication line configuration
Communication line category: TCP/IP-TCP, TCP Redundant.
IP address (addresses) is set according to a network configuration of a specific Siemens SIMATIC device.
The port number is 102 (according to specification RFC 1006).
The line number is not used, set to 1.
When a TCP Redundant communication line is configured, you can configure an IP address and port of a backup device. If a communication process loses the connection or is unable to connect to the device, it will switch periodically between the configured devices. The KOM process tries to connect to a primary device at first.
Note: Multiple IP addresses of primary/backup devices can also be configured (separated by commas or semicolons).
Note: if all of the stations are in StOFF mode (or in simulation), the TCP connection will be closed. Thus it is possible to control TCP communication from the event using an STSTAT tell command.
Line protocol parameters
A dialog window of communication line configuration - Protocol parameters tab.
They influence some optional protocol parameters.
The following line protocol parameters are defined:
Parameter | Meaning | Unit / size | Default value |
|---|---|---|---|
Rack | Siemens Simatic rack number. Rack 0 is most often used. | 0 to 7 | 0 |
Slot | Siemens Simatic slot number. Slot 2 is most often used. | 0 to 31 | 0 |
S7 Subnet ID-part 1 (hex) | S7 subnet address sent as a part of Remote TSAP if parameter Use long TSAP is set to True | 0x0 to 0xFFFF | 0 |
S7 Subnet ID-part 2 (hex) | S7 subnet address sent as a part of Remote TSAP if parameter Use long TSAP is set to True | 0x0 to 0xFFFF | 0 |
Use Secondary | The parameter allows the use of redundant PLCs, which may differ in the settings of some parameters (Rack, Slot, S7 Subnet ID). If its value is True, the primary and secondary parameters are used alternately when connecting to the PLC using the specified IP addresses. | - | False |
Connection Resource (hex) | Connection resource, it enters as MSB byte to the calculation of the value of Remote TSAP at initialization of ISO Connection-request. /TSK1/Sending CR-TPDU: CLASS=0, SRC-REF=0x0001, TPDU size=1024, SRC-TSAP=10-00, DST-TSAP=03-02 After changing the Connection resource from 3 to 2, the communication started working. Note: according to Siemens documentation, the Connection Resource can be:
| 0x0 to 0xFF | 3 |
Local TSAP (hex) | ISO Local TSAP (Transport Service Local Point). Source TSAP value during the initialization of ISO Connection-request. | 0x0 to 0xFFFF | 0x1000 |
Source Reference | ISO Source Reference. Value of SRC-REF during the initialization of ISO Connection-request. | 0 to 65535 | 1 |
Use long TSAP | Enables a long format of local and remote TSAP which is sent during the connection setup phase.
Short remote TSAP has the following format:
Long local TSAP is 28 bytes long. The last 2 bytes are higher and lower byte of parameter Local TSAP
| - | False |
MPI/Profibus Address | MPI/Profibus address sent as a part of Remote TSAP if parameter Use long TSAP is set to True | 0 to 126 | 1 |
ISO TPDU Size Variable Parameter | The maximum required size of ISO TPDU. The parameter value the initialization of ISO Connection-request. | 8192, 4096, 2048, 1024, 512, 256 or 128 bytes | 1024 bytes |
Nr. of Parallel Network Threads | Maximum parallel communication threads. Increase the value if there is a demand for more data read from the device in a shorter time. | 1 to 4 | 1 |
Cycle Time | The required time of one data reading cycle. | ms | 1000 ms |
Message Timeout | Maximal wait time on a reply from the device. | ms | 2500 ms |
Inter Message Delay | Delay before sending a data request. When a high data transfer rate is required, set 0 ms. | sec.ms | 20 ms |
Reconnect Delay | Delay before reconnection to the device if the connection has failed or some communication error has occurred. | sec.ms | 2 sec |
Connection Error Timeout | When Timeout passes and communication error occurs in all threads, a communication error status is set on the stations. The FALSE state is set on the communication line. | sec.ms | 20 sec |
S7 PDU Size | Maximum PDU in bytes at S7 communication with the device. | 240, 480, 960 bytes | 480 bytes |
Tcp No Delay | Setting "Tcp No Delay" parameter causes the low-level socket option TCP_NODELAY to be set, thus turning off the default packet coalesce feature. | - | False |
Debug Values | Activates debug info about the received values of I/O tags. Use this parameter only when communication must be debugged because it highly uses CPU and slows down the communication. | YES/NO | NO |
Debug I/O Binary Packets Info | Activates debug info about the binary content of packets. Use this parameter only when communication must be debugged because it highly uses CPU and slows down the communication. | YES/NO | NO |
Debug Requests Info | Activates basic debug info about requested data. | YES/NO | YES |
Debug Answers Info | Activates basic debug info about received packets. | YES/NO | YES |