Reference Manual

PMAC 2 Software Reference

82 PMAC I-Variable Specifiation

Ix26 Motor x Home Offset

Range

-8,388,608 .. 8,388,607

Units

1/16 Count

Default

Remarks

Ix26 specifies the relative distance of the Motor x zero position to either the trigger position

of a homing search move, or the zero position of an absolute sensor.

If Ix10 is set to 0, PMAC presumes the motor uses an incremental sensor and sets motor

position to 0 on power-up/reset. A homing search move is then required to establish the true

machine zero position.

In the homing search move, PMAC moves the motor until it sees a pre-defined trigger

condition, either an input trigger defined by Encoder I-variables 2 and 3 for the servo

interface channel addressed by Ix25, or the exceeding of the warning following error as set

by Ix12.

In the post-trigger part of the homing search move, the motor will stop a distance of Ix26

from the position at which it found the trigger, and call this commanded location as motor

position zero.

This permits the motor zero position to be at a different location from the home trigger

position, particularly useful when using an overtravel limit as a home flag (offsetting out of

the limit before re-enabling the limit input as a limit). If large enough (greater than 1/2 times

home speed times accel time) it permits a homing move without any reversal of direction.

If Ix10 is greater than 0, PMAC reads the sensor specified by Ix10 for the motor’s absolute

position. In this case, it subtracts Ix26 from the sensor position to calculate absolute motor

position. This is especially desirable if the zero position of the sensor is outside the region of

travel, as it is for an MLDT.

The units of this parameter are 1/16 of a count, so the value should be 16 times the number of

counts between the trigger position and the home zero position.

Example

If you wish your motor zero position to be 500 counts in the negative direction from the

home trigger position, you would set Ix26 to -500 * 16 = -8000.