Rockwell Automation 2080-LC50 Micro830 and Micro850 Programmable Controllers User Manual - Manual (Page 122)

108 Rockwell Automation Publication 2080-UM002F-EN-E - December 2013
Chapter 7 Motion Control with PTO and PWM
MC_HOME_REF_PULSE
For Homing against Lower Limit switch, one positive home offset can be
configured; for Homing against Upper Limit switch, one negative home offset
can be configured.
MC_HOME_REF_PULSE (3) homing procedure performs a homing
operation against Limit switch, plus fine Ref Pulse signal. The actual motion
sequence is dependent on the limit switch configuration, and the actual status for
the switches before homing starts—that is, when the MC_Home function block
is issued.
Scenario 1: Moving part at right (positive) side of Lower Limit switch before
homing starts
The homing motion sequence for this scenario is as follows:
1. Moving part moves to its left side (in negative direction);
2. When Lower Limit switch is detected, the moving part decelerates to stop,
or stops immediately, according to Limit Switch Hard Stop configuration;
3. Moving part moves back (in positive direction) in creep velocity to detect
Lower Limit switch On
→ Off edge;
4. Once Lower Limit switch On
→ Off edge is detected, start to detect first
Ref Pulse signal;
5. Once the first Ref Pulse signal comes, record the position as the
mechanical home position, and decelerate to stop;
6. Move to the configured home position. The mechanical home position
recorded during moving back sequence, plus the home offset configured
for the axis through the Connected Components Workbench software.
Scenario 2: Moving part on Lower Limit switch before homing starts
The homing motion sequence for this scenario is as follows:
1. Moving part moves to its right side(in Positive direction) in creep velocity
to detect Lower Limit switch On
→ Off edge;
2. Once Lower Limit switch On
→ Off edge is detected, start to detect first
Ref Pulse signal;
3. Once the first Ref Pulse signal comes, record the position as the
mechanical home position, and decelerate to stop;
IMPORTANT If Lower Limit switch or Ref Pulse is not configured as Enabled,
MC_HOME_REF_PULSE (3) homing fails (ErrorID: MC_FB_ERR_PARAM).