Description
Routing is the transfer of data beyond network boundaries. In this case you can send data from a sender to a receiver over various networks. For this you need special device technology that provides this functionality.
Data Record Routing is an extension of "normal routing" and is used for drives, for example and by SIMATIC PDM when the programming device is not connected directly to the PROFIBUS DP subnet to which the target device is also connected, but to the PROFINET interface of the CPU, for example.
The data sent with data record routing includes the parameter assignment of the field devices participating (slaves) and also device-specific information (setpoint values and limit values, for example). In data record routing, the structure of the target address depends on the data content, that is on the slave for which the data is destined.
With the PG you can use data record routing to read and edit a parameter record already on the field device or send it to the field device if the PG is already assigned as target slave to another subnet.
The field devices themselves do not have to support data record routing, because these devices do not forward the information content.
The following S7-300 CPUs and components of distributed IO devices support data record routing:
CPU
Version
CPU 313C-2 DP
V3.3
CPU 314C-2 DP
V3.3
CPU 314C-2 PN/DP
V3.3
CPU 315-2 DP
V3.0
CPU 315F-2 DP
V3.0
CPU 315-2 PN/DP
V3.1
CPU 315F-2 PN/DP
V3.1
CPU 317-2 DP
V3.3
CPU 317F-2 DP
V3.3
CPU 317-2 PN/DP
V3.1
CPU 317F-2 PN/DP
V3.1
CPU 319-3 PN/DP
V2.7
CPU 319F-3 PN/DP
V2.7
IM154-8 PN/DP CPU
V3.2
IM154-8F PN/DP CPU
V3.2
IM154-8FX PN/DP CPU
V3.2
IM151-8 PN/DP CPU
V2.7
IM151-8F PN/DP CPU
V2.7
Table 01
S7-400 CPUs firmware version V5.1 onwards support data record routing. For this the CPUs must also be configured in a higher firmware version.
CPU
Version
CPU 412-1
V5.1
CPU 412-2 DP
V5.1
CPU 412-2 PN
V6.0
CPU 414-2 DP
V5.1
CPU 414-3 DP
V5.1
CPU 414-3 PN/DP
V5.1
CPU 414F-3 PN/DP
V6.0
CPU 416-2 DP
V5.1
CPU 416-3 DP
V5.1
CPU 416F-3 DP
V5.1
CPU 416-3 PN/DP
V5.1
CPU 416F-3 PN/DP
V5.1
CPU 417-4
V5.1
CPU 412-5H PN/DP
V6.0
CPU 414-5H PN/DP
V6.0
CPU 416-5H PN/DP
V6.0
CPU 417-5H PN/DP
V6.0
Table 02
The following communications processors (CPs) support data record routing:
CP
Order number
Version
CP443-5 Extended
6GK7443-5DX02
V3.0
CP443-5 Extended
6GK7443-5DX03
V4.0
CP443-5 Extended
6GK7443-5DX04
V6.0
Table 03
The following gateways support data record routing:
CPU
Order number
IE/PB Link
6GK1411-5AA00
IE/PB Link
6GK1411-5AB00
IWLAN/PB Link
6GK1417-5AB00
IWLAN/PB Link
6GK1417-5AB01
Table 04
Additional Information Refer to the manuals of the CPUs to see whether or not the data record routing function is supported. The manuals of the above-mentioned CPUs, gateways and CPs are available in the following Entry IDs:
Manual
Entry ID
SIMATIC S7-300 CPU 31xC and CPU 31x:
Technical data
More information about data record routing is available in Entry IDs 19257092 and 7808062.
Note
Data record routing by means of the backplane bus is not supported for an I slave. The data for these modules cannot be routed over the backplane bus.
Additional Keywords Process device communication, Field device communication
Which modules can you use when implementing software redundancy?
Description Software Redundancy (SWR) is a software package for configuring fault-tolerant controllers with standard components. The controller part consists of standard CPUs of the S7-300 and S7-400 series. The redundancy link for synchronizing the redundant CPUs is achieved with standard communication mechanisms like CPs or via an MPI interface. Connection to I/O devices is via two redundant PROFIBUS DP segments to the ET-200M stations with redundant IM 153-2 interface modules. You can also implement Software Redundancy on WinAC RTX as from version 2008.
Note
More information is available in the function manual "Software Redundancy for SIMATIC S7" in Entry ID 1137637.
The following table lists modules that support software redundancy. The lowercase letter x is a wildcard character in the order numbers.
Note
The ET 200M stations must always be configured with active bus modules (6ES7195-7HB00-0XA0 or 6ES7195-7HC00-0XA0), even if the "Hot swapping of I/O modules" function is not possible with S7-300 CPUs.
What are the functional restrictions of old releases and firmware versions for the S7-400 CPUs operating in conjunction with the CP443-5 Extended V6.1?
Description This entry gives an overview of the functional restrictions for old releases and firmware versions of the S7-400 CPUs operating in conjunction with the CP443-5 Extended V6.1.
Restrictions for old releases of the S7-400 CPUs Table 01 shows S7-400 CPUs that are no longer supplied and which support or do not support the functions as listed below when operating in conjunction with the CP443-5 Extended V6.1:
No DPV1 functionality
No CiR functionality (DP slave, configurable extension)
No determination of bus topology from the user program
Max. number of external DP segments per station: 4
Number of CPs able to be operated: 8
Multicomputing
CPU
Order number
Release
Number of AG_SEND or AG_RECV calls
that can be operated in parallel
SYNC/FREEZE
CPU412
6ES7412-1XF01-0AB0
6ES7412-1XF02-0AB0
As from 2
As from 2
12/12
12/12
-
+
CPU413
6ES7413-1XG01-0AB0
6ES7413-1XG02-0AB0
As from 2
As from 1
12/12
12/12
-
+
CPU413-2
6ES7413-2XG01-0AB0
6ES7413-2XG02-0AB0
As from 2
As from 1
12/12
12/12
-
+
CPU414-1
6ES7414-1XG01-0AB0
6ES7414-1XG02-0AB0
As from 2
As from 2
12/12
12/12
-
+
CPU414-2
128 KB
6ES7414-2XG01-0AB0
6ES7414-2XG02-0AB0
As from 2
As from 2
12/12
12/12
-
+
CPU414-2
384 KB
6ES7414-2XJ00-0AB0
6ES7414-2XJ01-0AB0
As from 4
As from 2
12/12
12/12
-
+
CPU416-1
6ES7416-1XJ01-0AB0
6ES7416-1XJ02-0AB0
As from 2
As from 1
32/32
32/32
-
+
CPU416-2
0.8 MB
6ES7416-2XK00-0AB0
6ES7416-2XK01-0AB0
As from 4
As from 1
32/32
32/32
-
+
CPU416-2
1.6 MB
6ES7416-2XL00-0AB0
6ES7416-2XL01-0AB0
As from 4
As from 1
32/32
32/32
-
+
Table 01
Restrictions for S7-400 CPUs as from firmware version V3.1
CPU
Order number
6ES7...-0AB0
Firmware
version
Number of
AG_SEND or
AG_RECV calls
that can be operated
in parallel
SYNC/
FREEZE
DPV1
CiR/
HKiR
Enable /
disable
DP slaves
Determine
bus
topology
412
...412-1XF03...
As from V3.1
24/24
+
+
+
+
-
412-2
...412-2XG00...
As from V3.1
24/24
+
+
+
+
-
414-2
...414-2XG03...
As from V3.1
24/24
+
+
+
+
-
412-3
...414-3XJ00...
As from V3.1
24/24
+
+
+
+
-
414-4H
...414-4HJ00...
As from V3.1
24/24
-
+
+
-
-
416-2
...416-2XK02...
As from V3.1
64/64
+
+
+
+
-
416-3
...416-3XL00...
As from V3.1
64/64
+
+
+
+
-
416F-2
...416-2FK02...
As from V4.0
64/64
+
+
+
+
-
417-4
...417-4XL00...
As from V3.1
64/64
+
+
+
+
-
417-4H
...417-4HL00...
...417-4HL01...
As from V2.1
As from V3.1
64/64
64/64
-
-
-
+
+
+
-
-
-
-
Table 02
Which types of connection/protocols do the S7-300/400 CPUs and the CPs support by default?
Instructions: You can connect your controller to various subnetworks depending on which S7-300/400 CPU or CP you are using. The following types of connection/protocols can be used for these subnetworks.
Subnet
Connection types/Protocols
MPI
(Multiple Protocol Interface)
S7 communication (S7-300 only as a server)
GD communication (global data communication)
S7 basic communication
PROFIBUS
DP distributed I/O
(via an integrated port, CP342-5 and CP443-5 extended) FMS - Field bus message specification
(via CP343-5 and CP443-5 Basic) FDL - Field bus data link
(only via PROFIBUS CP)
S7 communication (S7-300 only as a server1))
Industrial Ethernet / PROFINET
S7 communication
(via an Ethernet CP or integrated PN interface)
ISO transport(via Ethernet CP) ISO-on-TCP (via Ethernet CP or an integrated PN interface) TCP (via Ethernet CP or an integrated PN interface) UDP (via Ethernet CP or an integrated PN interface)
E-mail (via Ethernet CP) FTP (via Ethernet CP) PROFINET IO (via Ethernet CP or an integrated PN interface) CBA (via Ethernet CP or an integrated PN interface) MODBUS TCP(via Ethernet CPs or integrated PN interface, see Entry ID: 226603042))
PTP (point-to-point)
RK 512
3964(R)
ASCII
various print drivers
Modbus (RTU) (master/slave) 2)
Data highway DF1 2) ...
1) S7 300: Client functionality only via CP342-5 from FW V5.2
2) These types of connection/protocol cannot be configured as standard in STEP 7 and must be installed afterwards.
The manuals on the Ethernet or PROFIBUS CPs tell you which communication services they support.
Furthermore, the following entries contain an overview of the communication services for S7-300/400 Ethernet CPs and S7-300/400 CPUs with integrated PN interface.
The "Technical Data" chapter of the manuals on the S7 300/400 CPUs describe which communication services can be used via the integrated interfaces in the controllers:
Note about S7 communication: The S7-300 supports S7 communication via the FB14/15 "GET/PUT", FB12/13 "BSEND/BRCV" or FB8/9 "USEND/URCV" function blocks. It works via:
the integrated PN interface with the function blocks from the Standard Library -> Communication Blocks.
CPs with the function blocks from the SIMATIC_NET_CP library.
In the S7-400, data exchange takes place via the SFB14/15 "GET/PUT", SFB12/13 "BSEND/BRCV" or SFB8/9 "USEND/URCV" function blocks. They can be found in the Standard Library -> System Function Block
Note about communication via the integrated PN interface of the CPU: Data exchange by means of TCP, ISO-on-TCP and UDP protocols takes place via open IE communication. The connection and data exchange are configured via the following communication blocks:
UDT 65 "TCON_PAR" with the data structure for assigning parameters to the connection
UDT 66 "TCON_ADR" with the data structure of the addressing parameters of the remote partner (UDP)
FB 65 "TCON" for establishing the connection
FB 66 "TCON" for clearing down the connection
FB 63 "TSEND" for transmitting data via TCP and ISO-on-TCP
FB 64 "TRCV" for receiving data via TCP and ISO-on-TCP
FB 67 "TUSEND" for transmitting data via UDP
FB 68 "TURCV" for receiving data via UDP
You can find further information about the programming and use of the individual types of connection in the following manuals.
Manual
Entry ID
System softwarefor S7-300/400
Systemandstandard functions
1214574
S7 basic communication
S7 communication
Open communication via Industrial Ethernet
PROFINET I/O (SFC 14/15 ("DPRD_DAT/DPWR_DAT")
S7-CPs for PROFIBUS
Configuration and commissioning
1158693
SEND/RECEIVE communication via an FDL connection
DP
FMS
S7-CPs for Industrial Ethernet
Configuration and commissioning
8777865
SEND/RECEIVE communication via
ISO-on-TCP, TCP, UDP or ISO transport connection
PROFINET I/O (FC 9/10 "PNIO_SEND/PNIO_RECV")
Information technology in a
SIMATIC S7 with CP 343–1 IT / CP 343–1 IT GX20 and CP 443–1 IT
Configuration Notes: The following table gives you an overview of the SIMATIC S7 modules that support the "Direct Data Exchange" function (internode communication) as I slave or DP master in the receive and send area.
Module
I slave
DP master
S7-300 CPUs
x
x
S7-400 CPUs
x1)
x1)
ET200 CPUs
BM147-1 CPU
x
x
BM147-2 CPU
x
x
IM151-7 CPU
x
x
IM151-7 CPU FO
x
x
IM151-7 F-CPU
x
x
IM154-8 CPU
x
x
PROFIBUS CPs
CP342-5
-
-
CP443-5 EXT
-
x
S7-400 IM modules
IM 467
-
x
IM 467 FO
-
x
WinAC RTX 2005 from SP2
-
x
x1) The "Direct Data Exchange" function is supported in Send mode from V3.0 and from in Receive mode from V1.1.
Note:
When implementing interface modules, support of the "Direct Data Exchange" (internode communication) function depends on the CPU used and not on the interface module itself.
Meaning of the numeric display in the NCM diagnostics buffer
QUESTION: How can I recognize the type of job from the numeric display in
the diagnostics buffer?
ANSWER: In the NCM diagnostics buffer of the communications processor,
the entries of the FMS services are displayed in numeric form. This
display identifies the jobs "READ", "WRITE", "REPORT", "STATUS" and
"IDENT". The corresponding assignments are shown in the table
below:
Configuration Notes: The CP 342-5 supports the
communication protocols S7, FDL, DP and
PG/OP. The following table lists some of the advantages and
disadvantages of the protocols.
Protocol
Advantages
Disadvantages
DP
Very fast communication.
Flexible implementation even with third-party systems.
Data transfer with acknowledgment.
Access without function call for small amounts or inconsistent
data.
The utility is suitable only for small data volumes (<=244
bytes).
Can only transfer static data.
Relatively complicated configuration.
FDL
Very fast communication.
Data is transferred consistently.
Both Multicast and Broadcast functions are
possible.
Only suitable for small data volumes (<=236 bytes)
Transfer is not acknowledged. User acknowledgment requires
evaluation of the message by the program.
More program resources are required to administer the data and
also the connection partners, because of the SEND/RECEIVE program
interface.
S7
Communication configuration not necessary.
Data can be transferred dynamically and variably.
Connection resources can be controlled by the application in
the PLC.
Can only be used for communication between SIMATIC S7
stations.
PG/OP
Teleprogramming possible.
Internetwork implementation of PG communication possible
through routing.
No protocol for module
communication.
Different block behavior of the FC5 and FC50 for Ind. Ethernet S7 300 CPs
QUESTION:
Doe the blocks FC5 (PLC_ SEND) and FC50 (PLC_LSEND) behave
differently with respect to the DONE bit?
ANSWER:
Yes, the block "PLC_SEND" (FC5 V1.2) keeps the DONE bit at TRUE
just for one cycle. The block "PLC_LSEND" (FC50 V 3.0) keeps it at
TRUE until a new order is started. This concerns only the S7 300
CPs up to CP343-1 (MLFB: 6GK7343-1EX10-0XE0). S7 400 CPs and more
recent CPs of the S7 300 series are not affected by this
behavior.
Note that for the Startup procedure the first call of the
"PLC_LSEND" without order ("ACT" is TRUE) also keeps the DONE at
0.
What are the requirements for using the S7 routing function and which modules can you implement?
Description From STEP 7 V5.0 SP3 HF3 onwards you can reach ST stations online over and beyond subnet limits with the PG/PC, in order, for example, to load user programs or a hardware configuration or in order to execute test and diagnostic functions. You can connect a PG/PC at any place within the network and connect online to any stations which are reached through gateways.
Gateway
The gateway from a subnet to one or more other subnets is in a SIMATIC station that has interfaces to the subnets concerned.
Requirements
At least STEP 7 V5.0 SP3 HF3 is installed on the PG/PC for configuration and use of the S7 routing function.
An interface (Industrial Ethernet or PROFIBUS PC CP) is installed in the PG/PC to establish a connection to the gateway. You can use PROFIBUS PC CPs 55xx and 56xx. You can use any NDIS-compatible Ethernet network card (3COM, CP1613, for example) as Industrial Ethernet interface in the PG/PC.
The associated communications modules of the station support the S7 routing function.
The network configuration does not go across project boundaries.
Both the modules and the PG or PC are loaded with the configuration information that contains the latest "knowledge" about the complete network configuration of the project. Technical background All the modules associated with the gateway must receive information about which subnets can be reached over which routes (= routing information).
Note The lists below have been updated with the modules of the hardware catalog of STEP 7 V5.4 SP2. This means that older modules which support the S7 routing function are listed in the tables, but are not necessarily included in the hardware catalog of the latest versions of STEP 7.
SIMATIC S7-CPUs The list below gives an overview of the SIMATIC S7 CPUs that support the S7 Routing function.
SIMATIC S7 FM modules The list below gives an overview of the SIMATIC S7 FM modules that support the S7 Routing function.
FM
Version
Order number
FM 356-4 V5.0
V5.0
6ES7356-4BM00-0AE0
FM 356-4 V5.0
V5.0
6ES7356-4BN00-0AE0
FM 456-2
V5.0
6ES7456-2AA00-0AB0
Table 01
Gateways The list below gives an overview of the gateways that support the S7 Routing function.
Link
Version
Order number
IE/PB Link
as from V1.0
6GK1411-5AA00
IE/PB Link PNIO
as from V1.0
6GK1411-5AB00
IWLAN/PB Link PNIO
as from V1.1
6GK1417-5AB00
IWLAN/PB Link PNIO
as from V1.1
6GK1417-5AB01
Table 02
SIMATIC S7 IM modules The list below gives an overview of the SIMATIC S7 IM modules that support the S7 Routing function.
IM
Version
Order number
IM 467
as of V2.0
6ES7467-5GJ02-0AB0
IM 467 FO
as of V2.0
6ES7467-5FJ00-0AB0
Table 03
SIMATIC WinAC RTX, WinAC Slot and WinAC MP The list below gives an overview of SIMATIC WinAC RTX, WinAC Slot and WinAC MP that support the S7 Routing function.
Description: At field level, protocols are not suitable for the PROFIBUS with a large number of services or complicated data processing, because the bus cycle time and response time required cannot be reached.
The PROFIBUS-DP protocol (distributed I/O) was developed specially to cover the field level in the automation hierarchy. The basic feature of the PROFIBUS-DP is that user data is displayed in the form of a cyclic data image. Here, object-oriented interfaces as used in the FMS or S7 protocol are avoided completely. The principle of the PROFIBUS-DP communication is a master-slave system. A master polls one or more slaves cyclically.
Instead of the user interface at Layer 7 (ISO-OSI reference model) of the DP protocol, there is the user interface that is based directly on Layer 2 (ISO-OSI reference model), i.e. on FDL, as standard application together with the DDLM (Direct Data Link Mapper).
There are two different types of DP master:
- Master Class 1: controls the process cyclically
- Master Class 2: device parameterization and diagnostics
Since there are no differences at Layer 2 for all the PROFIBUS protocols, all the protocols can be operated in parallel in one PROFIBUS network.
Position in the ISO-OSI reference model:
( 46 KB )
Fig. 01 - Position in the ISO-OSI reference model
In the model, the FDL connection occupies layers 1 and 2. Layer 2 is designated the FDL layer (Fieldbus Data Link) with PROFIBUS. Above layer 2 there is another specific interface that can be assigned to layer 4. All the other layers of the OSI reference model are not marked.
The message formats of the PROFIBUS Layer 2 permit high transfer reliability for FDL communication (Hamming Distance HD=4). Messages in which errors are detected are repeated automatically.
DP protocol services:
Service
Description
Data services
For reading or writing data of the parameterized distributed I/O. If a station is parameterized as slave, user data also can be made available to a master in this way.
Diagnostics services
For diagnosing a DP slave or DP master according to the job parameterized.
Control services
Permits sending of control jobs to a PROFIBUS-DP node in the following form:
- Operating mode changes
- Read jobs for inputs/outputs of other nodes
- Sending of global control commands
Advantages of the DP protocol:
Very fast communication protocol, due to close hardware proximity.
Can be used with third-party systems.
Acknowledged data transfer.
Disadvantages of the DP protocol:
Only suitable for transferring small data volumes (<=244 bytes).
Can only transmit static data lengths.
Relatively high configuration workload.
Note: General information on communication via SIMATIC S7 and other information on the DP protocol is available in Entry ID: 20982954.
Description: In the original form of the PROFIBUS specification, another protocol was specified alongside the FDL protocol, the FMS protocol. This protocol was designed to take into account high-quality hierarchical systems in addition to the field devices.
To achieve this, a part of the MMS (Manufacturing Message Specification) originating from the MAP communication model was also fulfilled in addition to the field device link. This overall model is the Fieldbus Message Specification (FMS).
Layers 3 to 6 are not marked in PROFIBUS. The user layer is Layer 2. The Lower Layer Interface (LLI) was developed for the FMS protocol for Layer 7. Implemented in this LLI for the FMS protocol are the functions of non-existent layers, such as connection setup and clear-down.
The FMS protocol is object-oriented. All the data is transferred in the form of manufacturer-independent, standardized communication objects. Access to each object is via Index or Name.
Position in the ISO-OSI reference model:
( 46 KB )
Fig. 01 - Position in the ISO-OSI reference model
Protocol services:
Type of service
Description
Productive services
Services for processing objects of an application process.
Management services
Services that refer to the management of a communication system.
Quantity framework:
Parameters
Value range
Number of possible
communication variables
For S7-300 up to:
- 256 server variables and
- 256 variable descriptions that can be loaded by the partner
The variables are freely distributable over all configurable FMS connections.
For S7-400 up to:
- 512 server variables and
- 2640 variable descriptions that can be loaded by the partner
The variables are freely distributable over all configurable FMS connections.
Interface
Layer 2
Number of possible
connections
Up to 16 per S7-300 CP
Up to 64 per S7-400 CP
Advantages of the FMS connection:
Acknowledged data transfer.
Can be used flexibly in systems of other makes.
Possible to access individual variables or structure elements.
Connections possible to slaves and masters.
Disadvantages of the FMS connection:
Not very high performance due to large overhead of management information.
High configuration workload, because all the variables have to be defined symbolically, for example.
Note: General information on communication via SIMATIC S7 is available in Entry ID: 20982954.
What properties, advantages and special features does the S7 protocol offer?
Description: All SIMATIC S7 and C7 controllers have integrated S7 communication services with which the user program can read and write data. The S7-400 controllers use SFBs, the S7-300 and C7 controllers use FBs. These functions are available to you regardless of the bus system used, so that you can use S7 communication via Industrial Ethernet, PROFIBUS or MPI.
The S7 Protocol can be inserted as follows in the ISO-OSI reference model:
( 46 KB )
Fig. 01 - Position in the ISO-OSI reference model
S7 protocol services:
Services
Description
PUT / GET
A unidirectional read/write service for transferring small volumes of data to and from a station.
USEND / URCV
A bidirectional uncoordinated service for transferring medium-sized volumes of data between two stations.
BSEND / BRCV
A bidirectional block-oriented service for transferring large volumes of data between two stations.
Service properties: The S7 protocol permits transfer of data from 1 byte to 64 Kbytes. The volume spectrum depends on the service and hardware used.
Service / Properties
BSEND / BRCV
USEND / URCV
PUT / GET
Max. data length
S7-300 / S7-400
32 KB / 64 KB 1)
160 bytes / 440 bytes 2)
160 bytes / 400 bytes 2)
Possible address ranges
S7-300 / S7-400
M, D/M, T, C, I, Q, D
M, D/M, T, C, I, Q, D
M, D/M, T, C, I, Q, D
Data consistency
S7-300 / S7-400
Total length per job 4)
Total length per job 4)
8-32 bytes / 32 bytes to total length 3,4)
Communication concept
Client / Client
Client / Client
Client / Server
Max. number of connections
See CPU specification
See CPU specification
See CPU specification
Blocks
S7-300 / S7-400
FB/SFB 12 "BSEND"
FB/SFB 13 "BRCV"
FB/SFB 8 "USEND"
FB/SFB 9 "URCV"
FB/SFB 15 "PUT"
FB/SFB 14 "GET"
1) Corresponds to the max. length of a data block of the system concerned in each case. 2) Corresponds to the total volume of user data for the SFB / FB in the case of Industrial Ethernet. 3) Depending on the CPU used. 4) In the user program you must make sure that the data block is not modified during data transfer.
Advantages of the S7 protocol:
Independent of the bus medium (PROFIBUS, Industrial Ethernet (ISO or TOP), MPI).
Can be used on all S7 data areas.
Transfer of up to 64Kbytes in one job.
Level 7 protocol ensures automatic acknowledgment of the data records.
Low processor and bus load during transfer of large volumes of data, because it is optimized for SIMATIC communication.
The S7 protocol is supported by all available S7 controllers and communication processors. Furthermore, PC systems with appropriate hardware and software support communication via the S7 protocol.
Notes:
Entry ID 20987358 provides a complete example of S7 communication with BSEND/BRCV via PROFIBUS.
General information on communication via SIMATIC S7 is available in Entry ID 20982954.
What properties, advantages and special features does the FDL protocol offer?
Description: The FDL protocol is the basic protocol on which every other PROFIBUS protocol is based. A great advantage of the protocol is its speed. Its proximity to hardware provides a correspondingly high message throughput rate. Another advantage is its flexibility. With its 4 services (of which SIMATIC S7 offers two as interfaces) it covers a broad spectrum of transfer options. The FDL protocol is supported by SIMATIC S7, S5 and PC systems each in connection with a PROFIBUS CP. Furthermore, SIMATIC S5 95U with PB interface also supports FDL communication.
Position in the ISO-OSI reference model
( 46 KB )
Fig. 01 - Position in the ISO-OSI reference model
In the model, the FDL connection occupies layers 1 and 2. Layer 2 is designated the FDL layer (Fieldbus Data Link) with PROFIBUS. Above layer 2 there is another specific interface that can be assigned to layer 4. All the other layers of the OSI reference model are not marked.
The message formats of the PROFIBUS Layer 2 permit high transfer reliability for FDL communication (Hamming Distance HD=4). Messages in which errors are detected are repeated automatically.
Types of data transfer FDL communication supports the following transfer services:
SDA - Send Data with Acknowledge
SDN - Send Data with no Acknowledge
SRD - Send and Request Data with Acknowledge
CSRD - Cyclic Send and Request Data
Only the SDA and SDN services are supported in the SIMATIC environment.
FDL connection types (in the SIMATIC configuration NetPro)
Connection type
Service
Description
Specified FDL connection
(point-to-point)
SDA
Local nodes and connection partners are defined by connection configuration. Receipt of data is acknowledged.
Unspecified FDL connection
(point-to-point with free Layer 2 access)
SDA
The local node is defined by connection configuration. The connection partner is addressed in the user program. Receipt of data is acknowledged.
Broadcast connection
SDN
An active node sends a message to all other nodes. Receipt of data is not acknowledged.
Multicast connection
SDN
An active node sends a message to a group of nodes. Receipt of data is not acknowledged.
Performance features of FDL communication
Parameters
S7-300
S7-400
Max. data length of a specified FDL connection (SDA)
240 bytes
240 bytes
Max. data length of an unspecified FDL connection (SDA)
236 bytes*1)
236 bytes*1)
Max. data length of a Broadcast or Multicast connection (SDN)
236 bytes*1)
236 bytes*1)
Possible address areas
E, A, M, D
E, A, M, D
Data consistency
240 bytes
240 bytes
Max. number of connections
Depends on CP*2)
Depends on CP*2)
Block types of services
FC
FC
*1) The connection partner is entered in the job header. The header consists of 4 bytes.
*2) The max. number of connections that can be operated depends on the CP used, the CPU used and the number of connections in the multiprotocol mode.
Capacity:
Parameters
SDA
SDN
Data area per job
1 - 240 bytes
1 - 236 bytes
Interface
Layer 2
Layer 2
Number of possible connections
Up to 16 per S7-300 CP
Up to 64 per S7-400 CP
Up to 16 per S7-300 CP
Up to 64 per S7-400 CP
Advantages of the FDL connection
Efficient and fast data transfer through slim architecture.
Easy connection of S5 and third-party systems to SIMATIC S7.
Disadvantages of the FDL connection
Additional resources in the user program for monitoring the data transfer and error messages of the communication blocks, as well as data management (the CP is the connection endpoint, i.e. the FDL protocol acknowledges the data only up to the CP layer. The user program is responsible for saving the data received).
Only suitable for transferring small data volumes (<=240 bytes)
Notes:
General information on communication via SIMATIC S7 is available in Entry ID: 20982954.
Entry ID: 20987711 includes a complete example of FDL communication with SDA service via PROFIBUS CP and S/R interface.
