Siemens SIMATIC NET SINAUT ST7 System Manual page 102

Introduction to the SINAUT ST7 system
2.11 SINAUT ST7sc SCADA Connect software
client later, ST7sc includes the "item buffering" technique that helps to avoid data loss on the
way to the OPC client, as follows:
● When the OPC "Data Access" interface that represents a process image is updated by
● When the OPC client is not available for brief or even longer periods or when OPC
While ST7sc normally creates only one "memory cell" per item and this always contains the
last state of the value of the item, when the item buffering technique is selected, a buffer is
created per item in which all changes of the relevant item are stored in chronological order
with their time stamps. These changes are stored until the individual changes have been
transferred to the OPC client.
The Item buffering technique is only possible with an HMI application that can process time-
stamped data even when the time stamp is several days old, for example after a long
connection breakdown.
SINAUT
ST7sc
Figure 2-32
Redundant application
SINAUT ST7sc allows attachment to a redundant client system. In this case, two ST7sc
systems are necessary. The data received from the stations is transferred parallel and
independently to both clients and data intended for the stations is received from these
clients.
The redundancy "intelligence" is a feature of the client:
● It ensures correct evaluation and synchronization of the simultaneously transferred data.
● It transfers data intended for the stations only once to one of the two ST7sc systems so
102
the SINAUT stations more quickly than the client can read it.
communication breaks down.
communication
"Data access" OPC server interface
1 2 3
ST7sc variable range
SINAUT message
coding
SINAUT
SINAUT
data
WAN
message
communication
System configuration with SINAUT ST7sc
that duplicate transfer is not necessary.
OPC
1 3 7 45 78 79
1a 3a 7a 78a 79a
1b 7b 78b 79b
1c 7c 79c
7d
7e
n
SINAUT message
decoding
SINAUT
data
message
SINAUT ST7 Station control system - System Manual
System Manual, 05/2007, C79000-G8976-C178-06