Homing - Siemens S7-1200 System Manual

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Technology instructions

9.3 Motion control

Use additional hardware limit switches if a mechanical endstop is located after the software

limit switches and there is a risk of mechanical damage.

Additional information

Your user program can override the hardware or software position limits by enabling or

disabling both hardware and software limits functionality. The selection is made from the

● To enable or disable the hardware limit functionality, access the "Active" tag (Bool) in the

DB path "<axis name>/Config/PositonLimits_HW". The state of the "Active" tag enables

or disables the use of hardware position limits.

● To enable or disable software position limit functionality, access "Active" tag (Bool) in the

DB path "<axis name>/Config/Position Limits_SW". The state of this "Active" tag enables

or disables the software position limits.

You can also modify the software position limits with your user program (for example, to add

flexibility for machine setup or to shorten machine change-over time). Your user program can

write new values to the " MinPosition " and " MaxPosition " tags (engineering units in Real

format) in the DB "<axis name>/Config/PositionLimits_SW".

Homing

Homing refers to the matching of the axis coordinates to the real, physical drive position. (If

the drive is currently at position x, the axis will be adjusted to be in position x.) For position-

controlled axes, the entries and displays for the position refer exactly to these axis

coordinates.

The agreement between the axis coordinates and the real situation is extremely important.

This step is necessary to ensure that the absolute target position of the axis is also achieved

exactly with the drive.

The MC_Home instruction initiates the homing of the axis.

S7-1200 Programmable controller

System Manual, 03/2014, A5E02486680-AG