Protocols

SINAUT ST1 protocol

This protocol is used in the SINAUT ST1 system, which is based on the SIMATIC S5 system. However, the SINAUT ST7 system also supports this protocol. Existing SINAUT ST1 systems can be further expanded with the SINAUT ST7 system, or existing system components can be replaced with ST7 devices.

Possible operating modes:

• Polling
• Polling with time slot procedure
• Spontaneous operation (for dialup networks)

Please note that only modems/transmission devices suitable for 11-bit asynchronous characters may be used in both polling modes. However, "spontaneous" mode supports transmission with both 11-bit and 10-bit asynchronous characters.

SINAUT ST7 protocol

This protocol is a more advanced version of the ST1 protocol. It enables SINAUT communication via both conventional and IP-based WANs. In addition, the addressing options have been extended:

• Up to 10,000 stations can be addressed
  (maximum of 254 for ST1)
• Message frames contain a source and a target address, (ST1 messsage frames only contain a source or a target address).

The ST7 protocol also supports "PG routing", i.e. remote programming and remote diagnostics via the WAN without interrupting SINAUT data traffic. PG routing and data traffic share the available bandwidth on the transmission path; PG routing is simply allocated a higher priority.

Possible operating mode in the IP-based WAN:

• Spontaneous mode

Possible operating modes in the conventional WAN:

• Polling,
• Polling with time-slot procedure,
• Spontaneous operation (for dialup networks)

DNP3 protocol

The DNP3 protocol (Distributed Network Protocol) is a standardized telecontrol protocol, independent of any manufacturer. It enables remote communication via both conventional and IP-based WANs.

Possible operating mode in the IP-based WAN:

• Spontaneous mode

Possible operating modes in the conventional WAN:

• Polling,
• Polling with time-slot procedure,
• Spontaneous operation (for dialup networks)

IEC protocol

The IEC 60870-5-101, -103, -104 are standardized vendor-independent protocols. They enable remote communication via both conventional and IP-based WANs. For implementing an RTU with IEC 60870-5 on the basis of SIMATIC, the CP 1243-1 IEC for SIMATIC S7-1200 and the SIPLUS RIC software bundle are offered.

Possible operating mode in the IP-based WAN:

• Spontaneous mode

Modes

• In polling mode, data exchange is controlled from the controller. It calls the connected terminals (including node terminals) in sequence. Terminals with modified data send this data as soon as they are called. Terminals with no modified data at the present time simply acknowledge the call. Data from the CPU to the terminals can be transferred at any time between the individual calls.
  The ST7 protocol supports direct data transmission between substations. During this type of communication, data is always exchanged via the polling control center TIM.
• Polling with time-slot procedure mode is used on a radio network on which the use of the radio frequency assigned by the registration authorities has to be shared with other operators. Typically, each operator has six seconds per minute to exchange data with its terminals. Once this time has elapsed, the frequency must be enabled for the next operator. During the allocated time slot, this type of polling operates in the same way as standard polling.
  The ST7 protocol supports direct data transmission between substations. During this type of communication, data is always exchanged via the polling control center TIM.
  In order to exactly observe the time slot, the polling control center TIM must be directly supplied with the DCF77 or GPS time.
• Spontaneous mode for data exchange on dial-up networks:
  Different priorities (normal, high or interrupt) can be assigned to the data of the station or node station for transmission in the dial-up network. Data to be sent by the control center always have the high priority. If data with a high or alarm priority is awaiting transmission, a dial-up connection is established immediately. At normal priority, data is initially saved in the terminals. This data is transmitted on the next connection that is made with the partner for any reason, for example if an item of information with a high or alarm priority is to be transmitted, or if the partner sets up a connection in order to exchange data.
  The message frames saved in the TIM are transmitted according to the FIFO principle, i.e. in the original chronological sequence, providing they are message frames with high or normal priority. If alarm message frames are present in the TIM buffer, these are always transmitted before the other message frames.
  Direct data transmission between substations is is possible with the ST7 protocol.
• Spontaneous operation in the IP-based WAN
  For transmission via an IP-based network, a permanent S7 connection is established in each case between two TIMs or between one TIM and the ST7cc/ST7sc. The two TIMs or the TIM and ST7cc/ST7sc exchange the data packages specific to SINAUT ST7 with application of the TCP/IP transport protocol. The transmission is performed with the resources of the S7 communication, in which the processing of the spontaneous data exchange depends on whether the transmitted volume of data is chargeable or not in the IP-based network.
  Networks without volume tariff:
  When data is transmitted, it is transferred immediately to the respective partner regardless of any priority.
  Data is transferred in accordance with the FIFO principle. This does not apply to message frames with "interrupt" priority. These are transferred before any other message frames that are available in the buffer.
  Networks with volume tariff:
  In an IP-based network such as the GPRS network, the priority of the individual data frames (normal, high or interrupt) is taken into consideration, as in the case of a dialup network. Data with normal priority is collected and transmitted in larger blocks, as soon as a specific size of block is achieved or, at the latest, when the specified TCP/IP Keep-alive interval has expired. This saves transmission volume because a reduced message frame overhead and fewer acknowledgment message frames are required. Important data with high or interrupt priority is transmitted immediately. Normal message frames that are buffered at this point are sent at the same time. Message frames with normal or high priority are transmitted in accordance with the FIFO principle.

Network configurations and topologies

All networks and all transmission media can be combined in any way in a telecontrol project – both with each other in "node structures", as well as in parallel in star topologies or in redundant configurations.

The graphics below show a selection of different topologies that can be implemented with the telecontrol components.

Basic topologies

Differently structured telecontrol networks can be implemented in the wide area network (WAN) based on the following four basic topologies.

Media versions

Depending on the support provided by the selected telecontrol protocol, various transmission media are available for these basic topologies, for example, dedicated line, private wireless networks, mobile wireless networks, dial-up networks (wireless/landline), DSL over Internet.

Some of these media versions are shown in the example of the star topology.

Combinations of basic topologies and media versions

Through a combination of several basic topologies of the same or different media versions, it is additionally possible to design more complex network topologies, even with redundant communication paths. This allows optimum adaptation to process requirements and to the existing infrastructure.