read
Read data synchronously from OPC DA groups or items
Description
and
S
= read(GObj
)
read
data for all the items contained in the S
= read(IObj
)dagroup
object,
GObj
, or for the vector of daitem
objects,
IObj
. The data is read from the OPC server’s cache, and
assigned to the structure S
.
You can synchronously read from the cache only if the Active
property is set to 'on'
for both the item and the group that
contains the item. A warning is issued if any of the objects passed to
read
are inactive. An inactive item is still returned in
S
, but the Quality
is set to
'BAD: Out of Service'
.
and
S
= read(GObj
,Src
)
read data from the source specified by S
= read(IObj
,Src
)Src
.
Src
can be 'cache'
or
'device'
. If Src
is
'device'
, data is returned directly from the device. If
Src
is 'cache'
, data is returned from the
OPC server's cache, which contains a copy of the device data. Note that the
Active
property is ignored when reading from
'device'
. Note also, that reading data from the device can be
slow.
When a read
operation succeeds, the Value, Quality, and TimeStamp properties of the associated items are updated to reflect
the values obtained from the read operation.
Examples
Input Arguments
Output Arguments
Version History
Introduced before R2006a