Sinaut ST1 refers to a Siemens telecontrol system based on the Simatic S5
automation system. Telecontrol interface modules (TIM) provide the telecontrol
interface for exchanging data with external devices using this protocol.
Sinaut ST1 3 can operate in three different modes:
- Polling mode
In polling mode, the control station interrogates all connected
substations which then transmit spontaneous data. No substation sends any data
without interrogation. Multi-point connections can only be implemented with
this half-duplex operation mode.
- Cyclic operation
This full-duplex transmission mode enables simultaneous data
transmission by both communication partners. Each telegram is acknowledged
by the distant terminal, which efficiently solves the issue of flow control.
This operation mode allows only point-to-point connections.
- Spontaneous mode
This operation mode enables data transmission via telecommunication
networks with dial-up modems. If a communication partner has data ready to
send, it automatically sets up a connection to the distant terminal,
sends
the data and immediately disconnects again if the distant terminal has no
data ready to send. As all relevant phone numbers are stored in the
communication partners' memory, they can open a line to all distant
terminals.
The telegram frames of the protocol comply with DIN 19244, FT1.2
format class which is also used in the IEC 60870-5-101 standard. In polling mode, up to 255
substations can be connected to a control station.
Unfortunately the number of information points that can be transmitted per
telegram is not uniquely defined and may be as follows:
Indication telegrams: |
1 or 2 byte payload
data per telegram which equals 16 or 32 indicating bits |
Analog value telegrams: |
8 or 16 byte
payload data per telegram which equals 4 or 8 measured values |
Counter value telegrams: |
4, 8 or 16 byte
payload data per telegram which equals 1, 2 or 4 counter values |
Command telegrams: |
principally 2
byte payload data per telegram which always equals 8 command bits |
The data telegram length must be chosen according to the required number of
data points, as the address space is limited to a maximum 255 telegram numbers.