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154 • Chapter 8 Hardware & Software Protection DMC-3425
Limit Switch Routine
The DMC-3425 provides forward and reverse limit switches that inhibit motion in the respective
direction. There is also a special label for automatic execution of a limit switch subroutine. The
#LIMSWI label specifies the start of the limit switch subroutine. This label causes the statements
following to be automatically executed if any limit switch is activated. The RE command ends the
subroutine and resumes the main program where it left off.
The state of the forward and reverse limit switches may also be interrogated or used in a conditional
statement. The _LR condition specifies the reverse limit and _LF specifies the forward limit. A or B
following _LR or _LF specifies the axis. The CN command can be used to configure the polarity of the
limit switches.
Limit Switch Example:
Instruction Interpretation
#A;JP #A;EN Dummy Program
#LIMSWI Limit Switch Utility
V1=_LFA Check state of forward limit
V2=_LRA Check state of reverse limit
JP#LF,V1=0 Jump to #LF if forward limit = low
JP#LR,V2=0 Jump to #LR if reverse limit = low
JP#END Jump to end
#LF #LF
MG "FORWARD LIMIT" Send message
STA;AMA Stop motion
PR-1000;BGA;AMA Move in reverse
JP#END End
#LR #LR
MG "REVERSE LIMIT" Send message
STA;AMA Stop motion
PR1000;BGA;AMA Move forward
#END End
RE Return to main program
NOTE: An applications program must be executing for #LIMSWI to function.