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This protocol supports a data reading/writing from the control PLC machines Siemens SIMATIC, types S7-300 and S7-400 which contain an ethernet interface for the communication S7 ISO over TCP.
Note: A 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 firmware upgrade of adapter to version V2.54 (31. march 2015) with adapter's BIOS version V2.39 (7. june 2011). When adapter's firmware was version V2.37 (8.august 2011), communication could not be correctly established.
Note: a communication with PLC machine Siemens LOGO was established. A part of memory that is accessible for read/write is the V area that is seen as DB1.
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Communication line configuration
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When the communication line is set as TCP Redundant you can configure IP address and port of a backup device. If a communication process lost the connection or is unable to connect to device, it will switch periodic between the configured devices. KOM process tries to connect to a primary device at first.
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A dialog window of communication line configuration - Protocol parameters tab.
They influence some optional protocol parameters.
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Parameter | Meaning | Unit / size | Default value |
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Rack | Siemens Simatic rack number. | 0 to 7 | 0 |
Slot | Siemens Simatic slot number. | 0 to 31 | 0 |
Connection Resource (hex) | Connection resource, it inputs as MSB byte to calculation of the value of Remote TSAP at initialization of ISO Connection-request. See description of parameter Use long TSAP. | 0x0 to 0xFF | 3 |
Local TSAP (hex) | ISO Local TSAP (Transport Service Local Point). Source TSAP value at initialization of ISO Connection-request. See description of parameter Use long TSAP. | 0x0 to 0xFFFF | 0x1000 |
Source Reference | ISO Source Reference. Value of SRC-REF at connection of ISO Connection-request. | 0 to 65535 | 1 |
Use long TSAP | Enables a long format of local and remote TSAP which is sent during connection setup phase. Short TSAP is 2 bytes long. Short local TSAP has following format:Short remote TSAP has following format:Long local TSAP is 28 bytes long. Last 2 bytes are higher and lower byte of parameter Local TSAP Full remote TSAP is 28 bytes long and it contains: | - | 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 |
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 adresa sent as a part of Remote TSAP, if parameter Use long TSAP is set to True | 0x0 to 0xFFFF | 0 |
ISO TPDU Size Variable Parameter | Maximum required size of ISO TPDU. The parameter value at 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 value if there is a request on more data read from device in shorter time. | 1 to 4 | 1 |
Cycle Time | Required time of one data reading cycle. | ms | 1000 ms |
Message Timeout | Maximal wait time on reply from other device. | ms | 2500 ms |
Inter Message Delay | Delay which is used before sending a data request. When high data transfer rate is required, set 0 ms. | sec.ms | 20 ms |
Reconnect Delay | Delay before reconnection to other 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. FALSE state is set on the communication line. | sec.ms | 20 sec |
S7 PDU Size | Maximum PDU in bytes at S7 communication with other device. | 240, 480, 960 bytes | 480 bytes |
Tcp No Delay | Setting Tcp No Delay parameter causes low level socket option TCP_NODELAY being set, thus turning off default packet coalesce feature. | - | False |
Debug Values | Activates a debug info about the loaded values of I/O tags. Use this parameter only when communication must be debug because it highly uses CPU and slows down the communication. | YES/NO | NO |
Debug I/O Binary Packets Info | Activates a debug info about a binary content of packets. Use this parameter only when communication must be debug because it highly uses CPU and slows down the communication. | YES/NO | NO |
Debug Requests Info | Activates a basic debug info about requested data. | YES/NO | YES |
Debug Answers Info | Activates a basic debug info about received packets. | YES/NO | YES |
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| komunikacna_stanica |
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Communication station configuration
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- Communication protocol: Siemens SIMATIC S7 ISO over TCP.
- No station address, no protocol parameters on station.
- Time parameter setting is ignored. See the line parameter Cycle Time.
- A time synchronization of device is not supported.
I/O tag configuration
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Possible I/O tag types: Ai, Ao, Ci, Co, Di, Dout, TiA, ToA, TiR, ToR, TxtI.
I/O tag address is compatible with Siemens SimaticNET OPC server.
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{;}{S7:[connectionname]}DB<no>,<type><address>{, <items>}
{;}{S7:[connectionname]}DI<no>,<type><address>{, <items>}
{;}{S7:[connectionname]}<object>{<type>}<address>{, <items>}
Where:
; | Optional parameter. It disables the I/O tag from communication, stops I/O tag address check when it is saved, and can be useful when the communication with device is activated or debugged. |
S7:[connectionname] | Optional parameter. It does not contains any useful information but it is supported only because of backward compatibility with Siemens SimaticNET OPC server. |
DB | Data block. S7 variable identifier from "Data block". |
DI | Instance data block. S7 variable identifier from " Instance data block". |
<no> | Number of "data block" or "instance data block". |
<object> | Specification of block or area in S7 PLC. Possible values: I | Input | Q | Output | PI | Peripheral input | PQ | Peripheral output | M | Memory bit | C | Counters (BCD coded integer numbers <0-999>) | T | Timers (BCD coded time values from intervals <0.00-9.99>, <00.0-99.9>, <000-999>, <0000-9.9990>) | S | SZL (System-ZustandsListen - system status lists) - lists with diagnostic information which are available on CPU family S7-300 and S7-400. Diagnostic information differs for various classes of PLC and details are described in manuals (e.g. System Software for S7-300/400 System and Standard Functions, Volume 1/2) Note: I/O tag S must be of TxtI type. |
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<type> | Data type of S7. It is not specified for T, C and S objects.
Identifier <type> | Description |
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X | Bit (boolean). Specify a bit number 0 to 7 - e.g. DB9,X8.3 | B | Byte (8 bits unsigned). | W | Word (16 bits unsigned). | D | Double word (32 bits unsigned). | CHAR | Character (8 bits signed). | INT | Integer (16 bits signed). | DINT | Double integer (32 bits signed). | REAL | Floating point number (32 bits according to IEEE754 standard). | LREAL | Long floating point number (64 bits according to IEEE754 standard). | STRING | String. Specify a string length. | DT | Date and Time, 8 bytes in BCD format. | TIME | Time (32 bits signed) in ms. | TOD | Time of day (32 bits unsigned) in ms. |
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<address> | Address of variable. Possible types:- Byte offset
- Byte offset.bit (only for X data type, bit number in the range of 0 to 7)
- Byte offset.String length (only for STRING data type, string length from 1 to 254 characters)
- Id.Index[.StringOffset[.StringLength]] - only for object S (system status list):
- Id and Index are 16-bit numbers in range 0-65535 defining ID of specific system status list and index of item in this list
- StringOffset and StringLength are byte offset (0..65535) and length (1..65535) of substring in answer, which will be parsed as a value of I/O tag.
Example: address S237.1.10.20 represents status list 237 (0x0111), index 1 (Identification of the module). S7-300 will answer to this request by a 36 byte-long string (bytes 0..35) in which bytes 10..29 (i.e. offset=10, length=20) represent "Order number of the module", e.g. '6GK7 342-5DA02-0XE0 '. Example of addresses:- DB10,W35
- DB8,X10.0
- DB1,REAL12
- DB5,STRING5.14
- T20
- C7
- MB11
- MDINT30
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<items> | number of elements for structured I/O tags with configured Destination column. Every read element (1,2,3 .. items) will be written to one item of destination column. Structured I/O tags are not supported for objects of type T (timers), C (counters) and S (system status lists) nor for data type STRING. Note: All items elements are read at once. If e.g. 100 elements of type D (double word) are configured, it means reading of a block of 400 bytes. If a smaller size of packet (S7 PDU size) is agreed on during establishment of connection, reading of this I/O tag will not be performed and trace file of line will contain an error message. Agreed S7 PDU size is minimum of size offered by D2000 (parameter S7 PDU Size) and supported size of specific device. Note: syntax of address when specifying number of elements is compatible with Siemens S7 OPC server (e.g. S7:[MyPLC]DB120,INT1050, 24), which facilitates simple transition from OPC communication to Siemens SIMATIC S7 ISO on TCP protokol by configuring a new line, a new station and then changing parent of I/O tags (e.g. via CSV or XML export and import).
Example of addresses:- DB10,W35, 20 a block of 20 words will be read (i.e. 40 bytes) from addresses 35-54
- DB8,X10.0, 100 a block of 100 bits will be read (i.e. 13 bytes) from addresses 10-22
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There have been reported cases when a communication with a device (specifically, Simatic S7-1200) was established, but after sending a read request the device didn't send required data but a packet with ResultCode = 0x8104, that is 33028 decimal.
According to http://stackoverflow.com/questions/23745407/libnodave-error-while-reading-from-siemens-s7-1200-0x8104 the problem is insufficient access rights. The cause is a new security option that was added to TIA Portal 12 and higher that by default disallows remote access to read/update blocks. Without this option disabled, only Siemens tools have access to the data.
Configuration: in TIA, under the properties for the CPU project, select "Protection"; there is an option for "Permit access with PUT/GET communications from remote partner" and set also "Access level" according to the following screenshot.
In case of TIA Portal version 14 the setting "Permit access with PUT/GET communications from remote partner" is on a dedicated tab "Connection mechanisms" under "Protection & Security":
![](/download/attachments/42713080/tia_cpu14.png?version=1&modificationDate=1510906090978&api=v2)
Siemens SIMATIC S7 ISO on TCP
Note on Siemens S7 1200/1500
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