Rockwell Automation FactoryTalk Transaction Manager User Guide - Manual (Page 106)

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FactoryTalk Transaction Manager User Guide
106
also a set of operators for both bit-wise and logical operations. Once an
expression has been defined, the syntax and semantics are checked to
determine if it can be evaluated at run time. Once the data points have been
collected, their current values are used to evaluate the expression. The
results are then passed to the database for processing.
Time Functions
The Expression Editor provides several functions for storing the current
time. Select time functions can be expressed in either Coordinated Universal
Time (UTC) or system local time.
The TimestampOf( ) function logs the time a data point is read. This may
differ from the time the transaction executed because the data point may
have a data valid time of greater than zero.
The TransTimestamp( )function returns the transaction execution time. This
may differ from the time the data was inserted into the database because
completed transactions may be buffered in cached transaction (*.rsl) files.
The MTimestampOf( ) and MTransTimestamp( )functions log the
millisecond portions of the two previous times. These can be stored in
separate columns, which permits accurate trend analysis for databases that
do not store time values to the millisecond.
The OPCTimeStampOf( ) and MOPCTimeStampOf( )functions return an
OPC timestamp value that indicates when the OPC data server (or
FactoryTalk data server) received (or read) the data from the controller. If
the data server is RSLinx Classic, this is when RSLinx Classic provided data
to FactoryTalk Transaction Manager. If the data server is RSLinx
Enterprise, this is the time when RSLinx Enterprise acquired the data from
the controller. This value is accurate to the nearest second.
Data Point Range and Advanced Functions
The Expression Editor supports a data point range syntax that compares a
data point value over a series of transactions. Each time the transaction runs,
a new value is added to the data range for a given transaction. The
expression is then evaluated using the range of values. This permits an