Siemens simatic et 200s Operating Instructions Manual page 322

1PosUniversal/Digital
7.6 Functions of the 1PosU
Principle
What You Do
Provide the control interface with data depending on the
MODE.
Check the POS_ACK feedback bit is at 0
Switch the START control bit from 0 to 1
Switch the START control bit from 1 to 0
Only when POS_ACK=0 can you start a new MODE.
If you start when a MODE is running, the 1PosU takes on the new motion and executes a change of direction, if
necessary.
Figure 7-5
322
Control and Feedback Signals with MODEs
Response of the 1PosU
The 1PosU sets the feedback bits POS_ACK = 1 and
POS_DONE = 0.
You can tell by this that the start has been detected by
1PosU and when POS_ERR = 0, the MODE is executed.
The MODE is not executed when POS_ERR = 1.
The 1PosU sets the feedback bit POS_ACK = 0
In the case of stopping, the reference point run, absolute
and relative positioning, the 1PosU sets the feedback bit
POS_DONE = 1 when the MODE is terminated without
errors.
When POS_ERR = 1 the MODE is terminated with an error.
Operating Instructions, 05/2007, A5E00124871-04
ET 200S Positioning