matrikon opc server for allen-bradley 用户手册
Matrikon OPC Server for Allen Bradley
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4.4.4 R
EQUESTED
D
ATA
T
YPE
All OPC items have a native (“canonical”) data type. That is to say, there is a default format to
the data that the server supplies for an item. When creating OPC items, client applications can
specify a requested data type for each item. The OPC server will attempt to covert any data from
the item to this format if possible. If the requested and canonical data types are incompatible,
then the server will fail to validate the item when it is added.
the data that the server supplies for an item. When creating OPC items, client applications can
specify a requested data type for each item. The OPC server will attempt to covert any data from
the item to this format if possible. If the requested and canonical data types are incompatible,
then the server will fail to validate the item when it is added.
4.4.5 A
CTIVE
S
TATE
Like groups, OPC items may be active or inactive. See the section on reading real-time values
for more information about this setting.
for more information about this setting.
4.4.6 V
ALIDATE THE
OPC I
TEMS
Choose “Validate Tags” from the File menu to check the created items for validity. Ta g Studio
will query the OPC server to determine whether the items are correct. A small red X next to an
item indicates that it did not validate properly. A green checkmark indicates that the item is
valid. A blue question mark indicates that the item has not been validated yet.
will query the OPC server to determine whether the items are correct. A small red X next to an
item indicates that it did not validate properly. A green checkmark indicates that the item is
valid. A blue question mark indicates that the item has not been validated yet.
4.5 R
EAD
R
EAL
-
TIME
V
ALUES
Once items are added to an OPC group, Matrikon OPC Explorer continually updates the display
for that group with real-time data. The data values appear in the list view on the right-hand side
of the window. Each item is listed along with its item ID, access path, active state, value, quality,
and timestamp.
for that group with real-time data. The data values appear in the list view on the right-hand side
of the window. Each item is listed along with its item ID, access path, active state, value, quality,
and timestamp.
When there are a number of groups created on an OPC server, use the group list view to navigate
between different groups and to view the items in those groups. Use the drop-down box to
navigate between the groups on different server connections.
between different groups and to view the items in those groups. Use the drop-down box to
navigate between the groups on different server connections.
4.5.1 U
PDATE
R
ATE
The OPC server tries to keep Explorer informed with values for an OPC group at the requested
update rate for that group. If the requested update rate is too fast for the server to handle then it
will return a revised update rate that it will use instead. Internally, the server tries to keep the
data items at least as “fresh” as indicated by the update rate. However, the server will send
values to the client no faster than the update rate in order to avoid overwhelming it.
update rate for that group. If the requested update rate is too fast for the server to handle then it
will return a revised update rate that it will use instead. Internally, the server tries to keep the
data items at least as “fresh” as indicated by the update rate. However, the server will send
values to the client no faster than the update rate in order to avoid overwhelming it.
4.5.2 A
CTIVE
S
TATE
OPC servers only update values for active items in active groups. When an individual item is set
inactive, the server stops sending updates for the item. When a group is set inactive, the server
stops sending values for any items in that group. Client applications (such as HMI applications)
can help to reduce the processing load on an OPC server by deactivating groups and items that
are not currently needed.
inactive, the server stops sending updates for the item. When a group is set inactive, the server
stops sending values for any items in that group. Client applications (such as HMI applications)
can help to reduce the processing load on an OPC server by deactivating groups and items that
are not currently needed.
Choose Activate/Deactivate from the Group or Item menus at any time to change the active state
of an OPC group or individual OPC items.
of an OPC group or individual OPC items.
4.5.3 D
ATA
D
ISPLAY