How MHI Preview and Run Requests Work	BKT 03-Nov-04

Step 1:  Select program source "External Analog" on the MTS controller main panel.

If the preview or run digital inputs from MHI are TRUE, an error dialog is generated and the program source reverts to the previous program source.  At this point, the Run Enable digital output to MHI is set to FALSE.  The Stop/Preview/Run button on the MTS controller main panel must remain in the stopped state in order to proceed to the next step below.


Step 2:  MHI issues a reset to the MTS controller as follows:

Step 2a: MHI first deactivates all three Gain Range digital outputs (issues all zeros) for any one of the six DOF channels.  Only one channel need be reset, although it does no harm to reset more than one channel.  This prepares the MTS controller for the actual reset event.  The state of the Run Enable digital output to MHI at this point is FALSE.

Step 2b: MHI then places non-zero values of Gain Range on all DOF channels.  It is this event that causes the state of MTS controller internal logic to reset.  Also, at this point the MTS controller will set the Run Enable digital output to MHI to TRUE if all of the following conditions are satisfied:
	Static lift autobalance sequence is not active.
	Table is not parked.
	MHI Stops 1, 2, and 3 are not active.
	The MTS e-stop chain is not active.
	All six external analog commands are less than +/-0.1 volt
	(this voltage tolerance may be changed by MTS to a smaller value in the future).
If any of these conditions are not met, the Run Enable digital output to MHI is set to FALSE.

If Step 2b above fails, Step 2a must be performed again before reattempting Step 2b.


Step 3:  MHI issues a preview request to the MTS controller.

If the Run Enable digital output to MHI is TRUE, and the Preview digital output from MHI transitions from FALSE to TRUE, the MTS controller will attempt to push the Preview button on the main panel.  When this happens, the MTS controller will start the preview process only if the Control Variable mode displayed on the main panel is "Velocity" or "Acceleration", because preview in displacement control mode is not supported.  An error dialog will be displayed if this condition is not satisfied.

If the preview request fails, the Run Enable digital output to MHI is set to FALSE.  Step 2 must be performed again before reattempting this step.

If the preview request succeeds, the Preview button is pressed.  If the Preview digital output from MHI transitions from TRUE to FALSE, the Stop button is pressed.  Also, a user sitting at the MTS controller can manually press the Stop button, if desired.  Subsequent transitions of the Preview digital output from MHI will cycle between Preview and Stop, respectively.


Step 4:  MHI issues a run request to the MTS controller.

If the Run Enable digital output to MHI is TRUE, and the Run digital output from MHI transitions from FALSE to TRUE, the MTS controller will attempt to push the Run button on the main panel.  When this happens, the MTS controller will start the run process only if the conditions listed in Step 2b above are satisfied.  An error dialog will be displayed if these conditions are not satisfied.

If the run request fails, the Run Enable digital output to MHI is set to FALSE.  Step 2 must be performed again before reattempting this step.

If the run request succeeds, the Run button is pressed.  If the Run digital output from MHI transitions from TRUE to FALSE, the Stop button is pressed.  Also, a user sitting at the MTS controller can manually press the Stop button, if desired.  Subsequent transitions of the Rundigital output from MHI will cycle between Run and Stop, respectively.

