102BTechnology instructions
9.3 Basic motion control
S7-1200 Programmable controller
350
System Manual, 11/2011, A5E02486680-05
9.3.2.3
MC_Home instruction
Table 9- 28 MC_Home instruction
LAD / FBD
SCL
Description
"MC_Home_DB"(
Axis:=_multi_fb_in_,
Execute:=_bool_in_,
Position:=_real_in_,
Mode:=_int_in_,
Done=>_bool_out_,
Busy=>_bool_out_,
CommandAborted=>_bool_out_,
Error=>_bool_out_,
ErrorID=>_word_out_,
ErrorInfo=>_word_out_);
Use the MC_Home instruction to match
the axis coordinates to the real, physical
drive position. Homing is required for
absolute positioning of the axis:
In order to use the MC_Home instruction,
the axis must first be enabled.
1
STEP 7 automatically creates the DB when you insert the instruction.
2
In the SCL example, "MC_Home_DB" is the name of the instance DB.
The following types of homing are available:
●
Direct homing absolute (Mode = 0): The current axis position is set to the value of
parameter "Position".
●
Direct homing relative (Mode = 1): The current axis position is offset by the value of
parameter "Position".
●
Passive homing (Mode = 2): During passive homing, the MC_Home instruction does not
carry out any homing motion. The traversing motion required for this step must be
implemented by the user via other motion control instructions. When the reference point
switch is detected, the axis is homed.
●
Active homing (Mode = 3): The homing procedure is executed automatically.
Table 9- 29 Parameters for the MC_Home instruction
Parameter and type
Data type
Description
Axis
IN
TO_Axis_PTO
Axis technology object
Execute
IN
Bool
Start of the task with a positive edge
Position
IN
Real
Mode = 0, 2, and 3 (Absolute position of axis after
completion of the homing operation)
Mode = 1 (Correction value for the current axis position)
Limit values: -1.0e
12
≤ Position ≤ 1.0e
12
