Description This entry shows you which hardware and software components you need to establish communication between SIMATIC S7 stations and third-party devices using the MODBUS RTU protocol. The SIMATIC S7 stations below can be used as Modbus Master (RTU) and Modbus Slave (RTU):
SIMATIC S7-300, ET 200M or S7-400 SIMATIC S7-300, ET 200M and S7-400 can be used as Modbus Master (RTU) or as Modbus Slave (RTU).
S7-300, ET 200M and S7-400 you need the hardware and software components below to connect a third-party device and establish communication with the MODBUS RTU protocol:
A serial CP
CP341 for S7-300 and ET 200M
CP441-2 for S7-400
The relevant loadable driver
The table below gives an overview of the hardware and software components.
Hardware and software components
The loadable drivers Modbus Master (RTU) and Modbus Slave (RTU) can be installed on the serial CP341 with the order numbers below:
The loadable drivers Modbus Master (RTU) and Modbus Slave (RTU) can be installed on the serial CP441-2 with the order numbers below:
Note For CP441-2 you need one of the following interface module:
6ES7963-1AA00-0AA0 with RS232 interface
6ES7963-2AA00-0AA0 with TTY interface
6ES7963-3AA00-0AA0 with RS422/RS485 interface
Loadable driver Modbus Master (RTU)
The loadable driver Modbus Master (RTU) for CP341 and CP441-2 is available for downloading in Entry ID: 27774018.
The license for the loadable driver Modbus Master (RTU) is available under the order numbers below:
6ES7870-1AA01-0YA0: the license delivery package includes the software, documentation and hardware dongle
6ES7870-1AA01-0YA1: the license delivery package includes only the hardware dongle
Loadable driver Modbus Slave (RTU)
The loadable driver Modbus Slave (RTU) for CP341 and CP441-2 is available for downloading in Entry ID: 27774276.
The license for the loadable driver Modbus Slave (RTU) is available under the order numbers below:
6ES7870-1AB01-0YA0: the license delivery package includes the software, documentation and hardware dongle
6ES7870-1AB01-0YA1: the license delivery package includes only the hardware dongle
More information about commissioning the loadable drivers Modbus Master (RTU) and Modbus Slave (RTU) is available in the manuals below.
SIMATIC S7-300/S7-400 Loadable Drivers for PtP CPs: MODBUS Protocol RTU Format, S7 is Master
How to download a loadable driver such as Modbus Master (RTU) into a CP341 that is connected to an S7-400 H system by means of an ET 200M is described in Entry ID: 17854293.
SIMATIC S7-1200 The SIMATIC S7-1200 station can be used as Modbus Master (RTU) or Modbus Slave (RTU).
In the S7-1200 you need one of the following communication modules to connect a third-party device and establish communication with the MODBUS RTU protocol.
CM 1241 RS422/485
CM 1241 RS485
CB 1241 RS485
CM 1241 RS232
More information about communication using the MODBUS RTU protocol is available in the manual in Entry ID: 36932465.
A sample program for establishing MODBUS-RTU communication for SIMATIC S7-1200 is available in Entry ID: 47756141.
SIMATIC ET 200S The SIMATIC ET 200S can be used as Modbus Master (RTU) or as Modbus Slave (RTU).
In the ET 200S you need a serial interface module ET 200S Modbus/USS to connect a third-party device and establish communication with the MODBUS RTU protocol.
Serial interface module
ET 200S 1SI
More information about the serial interface module ET 200S Modbus/USS is available in the manual in Entry ID: 9260793.
Note on security
Caution The functions and solutions described in this article confine themselves predominantly to the realization of the automation task. Furthermore, please take into account that corresponding protective measures have to be taken in the context of Industrial Security when connecting your equipment to other parts of the plant, the enterprise network or the internet. Further information can be found in Entry ID: 50203404.
Description On 1.10.2009 the ET 200M interface module with integrated FO interface, order number 6ES7153-2BB00-0XB0, was declared to be discontinued. The module is only available now as spare part. More information is available in Entry ID: 27031406.
Procedure An IM1513-2 FO can be replaced by a bus terminal and an ET 200M with RS485 interface.
In each case test the upgrade to ET 200S. When upgrading to ET 200S, check whether you have the option of changing to PROFINET. Since there is no compatible successor to the IM153-2 FO, we recommend that you desist from planning new plants based on the IM153-2 FO. This applies in particular when using Ex modules and F modules!
Options for replacing the interface modules
There are three different ET 200M modules with different functions. The IM153-2 HF can operate more modules than the IM153-2 FO.
The optical interfaces of the OBT and OLM modules differ in type. OBTs and the IM153-2 FO have simplex sockets. OLMs have BFOC sockets. More information about the optical interfaces is available in Entry ID: 35146578.
Plant extension with OBTs The plant topology changes from a purely optical network to an optical and electrical network. You can integrate ET 200M FO and OBTs in the optical network.
The IM153-2 HF can operate more modules. If the sum of the modules of multiple ET 200M FO stations is less than or equal to 12, then this IO can be combined with an IM153-2 HF in one station.
Plant extension with OLMs The plant topology changes from a purely optical network to an optical and electrical network. Only OLMs are integrated in the optical network and can be configured in a ring structure.
The IM153-2 HF can operate more modules. If the sum of the modules of multiple ET 200M FO stations is less than or equal to 12, then this IO can be combined with an IM153-2 HF in one station.
IMPORTANT Integration of ET 200M FO in an OM network has not been tested.
Procedure for changing the hardware configuration You must follow the procedure below for upgrading from an ET 200M FO to an ET 200M with RS485 interface.
Remove the fiber-optic cable from interface module IM153-2 FO.
Install the Optical Link Module OLM or the Optical Bus Terminal OBT in your control cabinet.
If you install an OLM, remove the simplex connector from the fibre-optic cable and mount the BFOC connector.
If you install an OBT, you do not need to change the connector, because the ET 200M FO and the OBT have the same optical interface.
Replace the interface module IM153-2 FO with the new interface module.
Connect the new interface module to the OLM or OBT with an electrical PROFIBUS bus cable.
In the case of a redundant setup, change the hardware configuration of the redundant interface module.
Change the hardware configuration of the STEP 7 project Proceed as follows to change the hardware configuration of the STEP 7 project.
In the hardware configuration you add a new DP slave to the existing PROFIBUS DP master system.
Configure the modules installed in the DP slave.
Delete the DP slave to be replaced.
Change the PROFIBUS address of the configured DP slave to the PROFIBUS address of the DP slave to be replaced.
In the Hardware Configuration you double-click the configured PROFIBUS DP master system to open the Properties dialog of the PROFIBUS DP master system.
Select the "General" tab and click the "Properties" button. The "Properties - PROFIBUS" dialog opens.
Switch to the "Network Settings" tab and click the "Options" button. In the "Options" dialog you select the "Cables" tab. Enable the "Take into account the following cable configuration" option and enter the number of OLMs and OBTs installed in the PROFIBUS DP master system and the cable length.
Save and compile the changed hardware configuration.
Download the hardware configuration to your target system.
Advantages of the upgrade
Investment protection through connection to electrical distributed IO
IM151-2 HF operate more modules and a greater address range per interface module
No need for distributed IO
Rapid upgrade time
Minimum upgrade costs
High network availability through redundant optical ring structure with OLMs
This concerns only the optical version of the ET 200M with order number 6ES7153-2BB00-0XB0. All other interface modules of the ET 200M are available without restrictions. There are no discontinuations planned for the time being.
Which manufacturer ID, in other words OUI (Organizationally Unique Identifier), does SIEMENS AG use for the MAC addresses of network-compatible devices?
Gateways like IE/PB Link, IWLAN/PB Link and IE/AS-Interface Link
Interface modules of ET 200M, ET 200pro and ET 200S
ET 200eco PN
The first 3 bytes of the MAC address describe the manufacturer ID, also known as the OUI (Organizationally Unique Identifier).
Up to now these modules above have been delivered with a MAC address in which the first three bytes have always been 08-00-06.
The manufacturer ID of the MAC addresses is administered by the IEEE (Institute of Electrical and Electronics Engineers). At the link below you can see which manufacturer ID or OUI the first three bytes of a MAC address describe.
SIEMENS AG uses the following manufacturer IDs or OUIs for the MAC addresses of the above-mentioned network-compatible devices.
Siemens IT Solutions and Services, SIS GO QM O
POB 2353 Fürth 90713
Siemens AG A&D ET
I IA SC EWK PU1, Östliche Rheinbrückenstraße 50
76181 Karlsruhe, Baden Württemberg
Confusion may arise in the following situations:
A network engineer uses a new module whose factory-set MAC address has the manufacturer ID 00-0E-8C or 00-1B-1B. From older modules he is used to factory-set MAC addresses having the manufacturer ID 08-00-06. Therefore he will look for a MAC address 08-00-06-xx-yy-zz which, however, he will not find.
Spare parts scenario: A module with a factory-set MAC address of 08-00-06-xx-yy-zz is defective and has to be replaced with a new module. It might be that the factory-set MAC address of the new module has the manufacturer ID 00-0E-8C or 00-1B-1B.
Which IO controllers and IO devices support the following functions: IRT, prioritized startup, MRP, PROFIenergy, Shared device, I device and clock-synchronized mode?
Description The Entry ID 49311792 gives you an overview of the PROFINET IO controllers and IO devices of SIMOTION and SINAMICS that support the PROFINET functions above.
Isochronous real-time communication (IRT) Synchronized transmission procedure for cyclic exchange of IRT data between PROFINET devices. There is a bandwidth reserved for the IRT data in the transmitter clock. The reserved bandwidth guarantees that the IRT data can be transmitted at reserved, clock-synchronized intervals even when the network is otherwise heavily loaded (with TCP/IP communication or additional real-time communication, for example).
Prioritized startup Prioritized startup is the PROFINET functionality for accelerating the startup of an IO device in a PROFINET IO system with RT and IRT communication.
The function cuts the time needed by the appropriately configured IO devices to get back into the cyclic user data communication in the cases below:
After return of power supply
After station return
After IO device enabling
Medium redundancy protocol (MRP) Medium redundancy is a function for ensuring that availability of networks and plants. Redundant transmission paths (ring topology) ensure that when one transmission path fails an alternative path is made available.
PROFIenergy Function for saving power in the process, during idle times, for example, through temporary switch-off of the encoder and load supply in the potential group via standard PROFIenergy commands.
More information about PROFIenergy is available in the manuals ready for downloading in the Entry IDs below.
Shared device IO device that makes its data available to multiple IO controllers.
I device Using the I device function you can use an IO controller also as IO device and thus establish a separate lower-level PROFINET IO subnetwork.
An I device can also be used as a shared device.
Clock-synchronized mode for process data Process data, transmission cycle via PROFINET IO and user program are synchronized with each other to achieve the highest deterministics. The input and output data of distributed IOs in the plant is captured and output simultaneously. The equidistant PROFINET IO cycle is the clock for this.
Which PROFINET nodes support automatic commissioning and the replace device without interchangeable medium function?
Description: IO devices that support the "Replace device without interchangeable medium" function can be replaced without the need for an interchangeable medium (Micro Memory Card, for example) with saved device name being slotted.
The replacement IO device no longer receives the device name from the interchangeable medium, but from the IO controller.
For this, the IO controller and the neighboring PROFINET devices of the replaced IO device must also support the "Replace device without interchangeable medium" function.
The IO controller uses the topology configured in STEP 7 to assign the device name and the neighbor relationships of the IO devices.
The IO controllers below support the "Replace device without interchangeable medium" function:
Configuration Notes: With the extended PROFINET diagnostics it is possible to have functions like the diagnostics and parameterization of integrated Ethernet interfaces (e.g. fiber-optic diagnostics and topology configuration). The PROFINET IO-Devices that support extended PROFINET diagnostics are configured in the Hardware Configuration in STEP 7. They are available in the hardware catalog and have additional ports e.g. interface modules as subslots in Slot 0.
Example: ET200S with and without PROFINET diagnostics
The following IO-Controllers support the extended PROFINET-Diagnostics:
SIMATIC NET PC-Software
SOFTNET PROFINET IO
Embedded and PC-based Automation
WinAC RTX 2008
CPU 414-3 PN/DP
CPU 416-3 PN/DP
CPU 416F-3 PN/DP
CPU 315-2 PN/DP
CPU 317-2 PN/DP
CPU 319-3 PN/DP
CPU 319F-3 PN/DP
Industrial Ethernet CPs
IM151-8 PN/DP CPU
IM151-8F PN/DP CPU
The following IO-Devices can use the extended PROFINET-Diagnostics:
The PROFINET IO devices that support the extended PROFINET diagnostics can only be operated on PROFINET IO controllers that likewise support the extended PROFINET diagnostics.
There is a migration GSDML file for some of the PROFINET IO devices listed above for operating the PROFINET IO device on a PROFINET IO controller that does not support the extended PROFINET diagnostics.
Example: PN/PN coupler
Note: The following applications provide a detailed description, including sample program, of the diagnostics options available in a PROFINET IO system.
"Diagnostic Methods for PROFINET Network Components (PROFINET IO, SNMP, WBM)" in Entry ID: 21566216
"PROFINET IO – Diagnostics Processing in the User Program"
in Entry ID: 24000238
What degree of accuracy can you obtain for plant-wide and segment-wide time stamping?
Description: If two signals change simultaneously at different stations of a plant, then the time stamp of the signal change may only differ at most by the amount of the accuracy class.
High-precision time stamping with an accuracy of 1 ms applies only between (and in) those ET 200M stations that are connected to the same DP interface of the PROFIBUS DP master, i.e. the ET 200M stations are connected to one and the same DP master system. High-precision time stamping with an accuracy of 1 ms therefore applies segment wide.
High-precision time stamping does not apply between ET 200M stations that are connected to different DP master systems. This also applies if the ET 200S stations are connected to different DP masters in one S7-400H system.
Fig. 01 shows the obtainable accuracy taking the example of a plant with SIMATIC components (CPU41x, CPU-H4, CP443-1, CP443-5, ET 200M).
Fig. 01: Accuracy classes of time stamping
Note: For setting high-precision time stamping, refer to the operating instructions of the distributed IO system ET 200M and observe all the notes regarding the components required and the parameters for time stamping and time synchronization. The manual is available for downloading in Entry ID 1142798.
Why do the analog input modules in ET200-M give the value 7FFFH for a few milliseconds after bus start-up?
The analog input modules (AI) as of release 4 need a little more time for the first conversion than the previous versions. You get the value 7FFFH until the analog modules are completely initialized. This state is displayed in the S7 diagnosis. An S7 diagnosis is valid when the contents of the 10th byte are "01H". Bit 2 "STOP mode" is set in byte 15 of the S7 diagnosis.
What options are provided by the new function for time stamping
with IM153-2BA00 and what are the requirements?
First of all, all the general conditions for time stamping of
digital process signals hold, see the manual "SIMATIC Process
Control System PCS 7 Engineering System V6.0", section 4.8
"10ms Timestamp" in Entry ID 15229448
Furthermore, there are more options available from module IM153-2
(MLFB 6ES7 153-2Bx00-0XB0):
Adjustable synchronization time/monitoring time of the time
Precision: 3 ms in the slave / 10ms cross-component in the
system – holds also when implementing I/Os that are not exclusively
Guarantee of precision requirements with a synchronization time
of the time message on the DP bus of 10 seconds (or less).
Other new functions can be used without impairing the precision
(e.g. synchronous operation).
Standardized behavior complying with the time stamp standard
(e.g. at startup and for error response).
Re Point 1: Notes on setting the synchronization time on
the DP slave:
Set the time across the system to the required value, i.e. if
you plan to time stamp with a precision of 3ms in the station or
10ms cross-station, you select 10 seconds. If a precision higher
than 10ms is sufficient, then select the next largest value: 1
min. Background: A cyclic time-of-day synchronization of
all the components in the station (Ethernet CPs, CPUs, DP master,
DP slaves, ...) demands performance which might be able to be
In any case, on the slave you set a time-of-day synchronization
interval that is greater or equal to the actual synchronization
interval. Background: The IM153-2BA00 monitors arrival of the
time messages in the triple cycle of the synchronization time. This
means that if once this monitoring time has expired no time message
has arrived, the IM issues an error message "Message failure,
INCOMING". If a time message then arrives again, the IM issues
the message "Message failure, OUTGOING". Therefore, if
you have set too small a synchronization time, you get both
messages in constant sequence.
Fig. 1: HW Config parameter mask for IM153-2BA00
Re Point 2: Notes on behavior complying with standards
and the associated difference to previous behavior:
After proper configuration, the Time Stamp function also starts
when there has been no prior arrival of a time message.
The internal IM clock is set to 1.1.1984; 0:00h at the moment
of initialization. Any time-stamped information before arrival of
the first time message is given a time greater than the
initialization time. Any time message that arrives after that sets
the clock to the current time. This is why you get the message
"Difference between internal clock time and synchronization
Each synchronization that arrives is determined as valid even
if a prior time master determines failure of its
synchronization and executes a substitute synchronization to its
slave. This then might result in slaves no longer working in
synchronization to different masters or CPUs. The components that
detects the failure must also generate an error message that IM is
not transmitting any more error messages.
Background: To avoid message surges from subordinate
components that all detect the same problem.
More information on this topic is available in the following
Entry IDs: "SIMATIC NET Time-of-day Functions of the
CP1613" – Entry ID 1683661 and "Meaning and function of
time stamping in the ET200M/IM153-2" – Entry ID
Now available, the "New IM 153-2 High Feature Interface
Module for ET200M" – Entry ID 14326542.
Which manuals for ET 200M are available for downloading in A&D Product Support?