246 Siemens Simatic S7 Driver Online Help
Process database block — individual units of instructions that receive, verify,
manipulate, and output process values. Process database blocks can also
compare a process value against an alarm limit and perform calculations based
on a specific process value.
SAC — the Scan, Alarm, and Control program (SAC) is a FIX/iFIX system task that
runs on a SCADA server. The primary task of SAC is to transmit and receive
data between the process database and the I/O driver’s common memory.
However, SAC also translates the data into the format expected by the process
database, examines the data against the alarm limits and generates alarm
messages, executes control logic, and detects exceptions.
Signal conditioning — the method by which a raw process data value is scaled.
Time-based scan time — a method of processing data that instructs SAC to retrieve
data at set time intervals. Use time-based scanning when your data changes
frequently.
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