Value, Time-Stamp and status with allocations

Value, Time-Stamp and status with allocations

What exactly is being mapped when using an allocation?

Generally an allocation can be used to transfer a variable value from PLC A to PLC B, even if this is a totally different brand.
Normally, (if no trigger variable is used) the allocation is executed spontaneously. As soon as the source variable changes, the same value will be written to the target variable.
With a trigger variable the allocation can be controlled. E.g. continiously when the triggervariable has the value "1" or at a rising edge of the trigger variable, the allocation is executed.
In both cases, only the value from the source variable is being written to the target variable, not the status and the time-stamp. With a spontaneous allocation however, the difference in timestamp of the source and target variable is only a few milliseconds.

This is a migrated post! Originally posted on 14.09.2007 by user markclemens. Please be aware that information can be outdated.