ADLINK PCI-8158 - Manual (Page 87)

Operation Theory 77
4.6 The Comparators
There are 5 counter comparators of each axis. Each comparator
has dedicated functions. They are:
1. Positive soft end-limit comparator to command counter
2. Negative soft end-limit comparator to command counter
3. Command and feedback error counter comparator
4. General comparator for all counters
5. Trigger comparator for all command and feedback
counters
4.6.1 Soft end-limit comparators
There are two comparators for end-limit function of each axis. We
call them for the soft end-limit comparators. One is for plus or pos-
itive end-limit and the other is for minus or negative end-limit. The
end-limit is to prevent machine crash when over traveling. We can
use the soft limit instead of a real end-limit switch. Notice that
these two comparators only compare the command position
counter. Once the command position is over the limited set inside
the positive or negative comparators, it will stop moving as it
touches the end-limit switch.
4.6.2 Command and feedback error counter comparators
This comparator is only for command and feedback counter error.
Users can use this comparator to check if the error is too big. It
can be set a action when this condition is met. The actions include
generating interrupt, immediately stop, and deceleration to stop.
4.6.3 General comparator
The general comparator let users to choose the source to com-
pare. It could be chosen from command, feedback position
counter, error counter or general counter. The compare methods
could be chosen by equal, greater than or less than with direc-
tional or directionless. Also, the action when condition is met can
be chosen from generating interrupt, stop motion or others.