Siemens Simovert Masterdrives Compendium page 756

08.2012
9.4.23 Homing mode [821]
WARNING
Siemens AG 6SE7087-6QX70 (Version AN)
SIMOVERT MASTERDRIVES
Mode 2 "homing" is only necessary with incremental encoders, i.e.
when using a resolver, optical sin/cos encoder or pulse encoder.
Homing is not necessary when using an absolute encoder or roll feed.
With incremental encoders, the axis must be moved to the home
position before a position control mode (setup, MDI, automatic) can be
started.
• Automatic reversal of the traversing direction does not take place
during the homing procedure if a hardware limit switch is reached.
Hardware limit switches must be evaluated by the external machine
control system and additionally - if they are safety-related - by the
hardware (see also the danger notice in "Commissioning the
technology").
• No monitoring takes place when a movement is started, although
the "axis referenced" status signal [ARFD] is active; this status bit
must be evaluated by the external machine control system.

You will find detailed information on homing mode in the chapter
entitled "Reference point approach" in the Function Description
of manual /1/.
When incremental position encoders are used, there is no relationship
between the measuring system (incremental encoder) and the
mechanical position of the axis when the controller is switched on. For
this reason, the axis must be moved to a defined home position each
time the system is switched on, i.e. in order to reference the axis.
There are two ways to reference the axis:
♦ With homing, the axis travels across a proximity switch (BERO)
(rough pulse) to the zero pulse (fine pulse) of the incremental
encoder. When the fine pulse is detected, the measuring system is
set to a defined coordinate, thereby establishing the absolute
position reference to the mechanical system.
♦ With "set home position", the coordinate is set immediately on
activation by the user program. The home position thus depends on
the mechanical position of the axis at the time the home position is
set.
In most cases, the homing procedure is used to reference the
measuring system, since this method is accurate to the nearest
increment.
"Set home position" is used if neither a rough pulse (proximity switch)
nor a fine pulse is available or if the application requires the axis to be
referenced at different positions.
Compendium Motion Control
Technology Option F01
9-65