Siemens SIMATICS PCS7 사용자 설명서
General/elementary telecontrol functions
14
Telecontrol protocols
General/elementary telecontrol functions
Telecontrol systems use special protocols to implement data
transmission between the control center and the outstations
(RTUs) at the process level for the automation functions on
site. These telecontrol protocols manage the secure and error-
free data transmission over the WAN even with a low band-
width and poor transmission quality.
transmission between the control center and the outstations
(RTUs) at the process level for the automation functions on
site. These telecontrol protocols manage the secure and error-
free data transmission over the WAN even with a low band-
width and poor transmission quality.
In addition to short transmission times for the information,
this task requires effective protection of the frames against:
this task requires effective protection of the frames against:
• Undetected bit errors
• Undetected frame errors resulting from synchronization
• Undetected frame errors resulting from synchronization
errors
• Undetected loss of information
• Frame falsification
• Segregation or fault in related information
• Frame falsification
• Segregation or fault in related information
This particularly applies to event-controlled frames over trans-
mission channels with a limited bandwidth and uncertain
noise response.
mission channels with a limited bandwidth and uncertain
noise response.
Since irregular bit sequences are compiled for data transmis-
sion, no limitation in codes must exist.
sion, no limitation in codes must exist.
Time tagging
When linking RTUs by means of SINAUT ST7, DNP3,
IEC 870-5-101 or IEC 870-5-104 telecontrol protocol, the raw
data in the outstations is provided with a time tag and trans-
mitted to the PCS 7 TeleControl OS (server/single station)
acting as control center. Adaptation, further processing, and
archiving are carried out here. This procedure is appropriate
for the event-based principle of operation of the telecontrol
protocol as well as the subsequent chronological processing
of data previously buffered in the outstation.
IEC 870-5-101 or IEC 870-5-104 telecontrol protocol, the raw
data in the outstations is provided with a time tag and trans-
mitted to the PCS 7 TeleControl OS (server/single station)
acting as control center. Adaptation, further processing, and
archiving are carried out here. This procedure is appropriate
for the event-based principle of operation of the telecontrol
protocol as well as the subsequent chronological processing
of data previously buffered in the outstation.
Clock synchronization
The PCS 7 TeleControl OS is the clock master for the RTUs
connected by means of SINAUT ST7, DNP3, IEC 870-5-101 or
IEC 870-5-104, and regularly synchronizes their date and time
via the telecontrol connection. Switching over between sum-
mertime and wintertime is also considered during the syn-
chronization.
connected by means of SINAUT ST7, DNP3, IEC 870-5-101 or
IEC 870-5-104, and regularly synchronizes their date and time
via the telecontrol connection. Switching over between sum-
mertime and wintertime is also considered during the syn-
chronization.
Data buffering
The SINAUT ST7, DNP3, IEC 870-5-101 and IEC 870-5-104
telecontrol protocols support reliable on-site intermediate
buffering of the data including time tag, e.g. if a communi-
cation path is faulty or a station has failed. In addition, inter-
mediate buffering of data can also be an effective means
for reducing connection costs in the dial-up network.
telecontrol protocols support reliable on-site intermediate
buffering of the data including time tag, e.g. if a communi-
cation path is faulty or a station has failed. In addition, inter-
mediate buffering of data can also be an effective means
for reducing connection costs in the dial-up network.
A data update for all participating communication partners
is performed automatically following debugging or restarting
of the failed station. Important events are not lost, and the
integrity of the control center archive is assured.
is performed automatically following debugging or restarting
of the failed station. Important events are not lost, and the
integrity of the control center archive is assured.
© Siemens AG 2011