Siemens simatic et 200s Operating Instructions Manual page 202

1PosSSI/Digital
5.6 Functions of the 1PosSSI/Digital
Interfaces to the Control Program and the Axis
To execute the function, the 1PosSSI/Digital has digital inputs as an interface to the axis,
encoder signals for the connection to an encoder and digital outputs to control the drive.
You can modify and monitor the types of motion (MODES) and functions (JOBs) with your
control program using control signals and feedback signals.
See also
Parameter List (Page 234)
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 1PosSSI/Digital takes on the new motion and executes a change of direction, if
necessary.
Figure 5-5
202
Control and Feedback Signals with MODEs
Response of the 1PosSSI/Digital
The 1PosSSI/Digital sets the feedback bits POS_ACK = 1
and POS_DONE = 0.
This indicates that the start of the 1PosSSI/Digital has been
detected and that the MODE is executed when
POS_ERR = 0.
The MODE is not executed when POS_ERR = 1.
The 1PosSSI/Digital sets the feedback bit POS_ACK = 0
In the case of stopping, absolute and relative positioning,
the 1PosSSI/Digital sets the feedback bit POS_DONE = 1
when the MODE it terminated without errors.
When POS_ERR = 1 the MODE is terminated with an error.
Operating Instructions, 05/2007, A5E00124871-04
ET 200S Positioning