Reference Guide

PMAC Quick Reference Guide
24 Installing and Configuring PMAC
Flags Power Supply (Optional)
Each channel of PMAC has four dedicated digital inputs on the machine connector: +LIMn, -LIMn
(overtravel limits), HMFLn (home flag), and FAULTn (amplifier fault). In most PMACs, these inputs
can be kept isolated from other circuits. A power supply from 12 to 24V can be used to power the
corresponding opto-isolators related to these inputs. This feature is not available in PMAC PC without
Option 1, PMAC VME or the PMAC STD board.
Overtravel Limits and Home Switches
When assigned for the dedicated uses, these signals provide important safety and accuracy functions.
+LIMn and -LIMn are direction-sensitive overtravel limits that must be actively held low (sourcing
current from the pins to ground) to permit motion in their direction. The direction sense of +LIMn and -
LIMn is as follows: +LIMn should be placed at the negative end of travel, and -LIMn should be placed at
the positive end of travel.
Disabling the Overtravel Limits Flags
If no overtravel limits are used, they must be disabled through a change to variable Ix25. On the terminal
window, the following commands will disable the limits functions for all eight motors. Select the motor
numbers as appropriate.
The OR ( | ) bit-by-bit function used here is accessible by pressing shift + ”\” in the computer’s
keyboard.
I125=I125|$20000 ;Motor #1
I225=I225|$20000 ;Motor #2
I325=I325|$20000 ;Motor #3
I425=I425|$20000 ;Motor #4
I525=I525|$20000 ;Motor #5
I625=I625|$20000 ;Motor #6
I725=I725|$20000 ;Motor #7
I825=I825|$20000 ;Motor #8
Types of Overtravel Limits
PMAC expects a closed-to-ground connection for the limits to not be considered on fault. This
arrangement provides a failsafe condition and therefore it cannot be reconfigured differently in PMAC.
Usually, a passive normally closed switch is used. If a proximity switch is needed instead, the following
type is recommended:
Related PMAC jumpers must be configured appropriately, following the corresponding PMAC Hardware
Reference manual.