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Subject: RE: motor record: continuously update limit switches
From: Mark Rivers <rivers@cars.uchicago.edu>
To: "'Konrad, Martin'" <konrad@frib.msu.edu>, "tech-talk@aps.anl.gov" <tech-talk@aps.anl.gov>, "sluiter@aps.anl.gov" <sluiter@aps.anl.gov>, "mooney@aps.anl.gov" <mooney@aps.anl.gov>, "sullivan@aps.anl.gov" <sullivan@aps.anl.gov>
Date: Thu, 25 Jul 2013 22:19:40 +0000
Hi Martin,

There are several fields that reflect the limit status of a motor.

HLS, RHLS, LLS and RLLS only update when you try to move the motor in the direction of the offending switch.

However, the MSTA field will update if you write 1 to the STUP field.  That reads the hardware status from the controller.  Bits 3 and 14 (numbering from 1 as in the motor record documentation) are the plus and minus limit switch status respectively.  For Model 3 drivers that continually poll the hardware and process the motor record on status changes MSTA will update without needing to process STUP.

Is your goal to make the user aware of the limit status by changing something in the GUI?  If so you can do this by having 2 other records that get their value from bits 3 and 14 of MSTA, and putting those records in the GUI.  Of course this does not work with the standard GUI screens in the motor module.

It would be nice if HLS, RHLS, LLS and RLLS reflected the actual limit status.  In fact the motor record documentation is wrong.  For HLS and RHLS it says:
 
" If either of these fields is nonzero, then the motor is at the positive-limit switch, where the positive sense is that of the user-coordinate system for HLS, and that of the raw (step-number) coordinate system for RHLS."

That is not true, it does not reflect the state of the switch.  It only reflects the error status if the switch is hit and the user tries to move in the direction of that switch.

Mark


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Konrad, Martin
Sent: Thursday, July 25, 2013 4:12 PM
To: tech-talk@aps.anl.gov; sluiter@aps.anl.gov; mooney@aps.anl.gov; sullivan@aps.anl.gov
Subject: motor record: continuously update limit switches

Hi!

I am dealing with a slightly unconventional motor setup where two limit
switches are used for two motor axes in the following way:

-limit switch 1 acts as the high limit for controller 1 and low limit
for controller 2
-limit switch 2 acts as the low limit for controller 1 and high limit
for controller 2

This means the status of the limit switches of an axis can change even
if its motor is stopped. The motor record does not seem to expected a
behavior like that - at least not with the Parker PC6K device support.
The limits are only updated while the motor is moving.

I tried a caput to the STUP field but that didn't have any effect. Is
there a way to force the motor record to update the status of the
switches? This might also be helpful for simple multi-axis operation
with a single home switch.

Any help is greatly appreciated,

Martin



References:
motor record: continuously update limit switches Konrad, Martin

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