National Instruments 7340 PCI Benutzerhandbuch

You can use software disabled limit and home inputs as general-purpose 
inputs. You can read the status of these inputs at any time and set and 
change their polarity as required.

Limit and home inputs are a per axis enhancement on the 7340 and are not 
required for basic motion control. These inputs are part of a system solution 
for complete motion control.

National Instruments recommends using limits for personal safety, as well as to 

protect the motion system.

For the end of travel limits to function correctly, the forward limit must be 
located at the forward or positive end of travel, and the reverse limit at the 
negative end of travel.

Failure to follow these guidelines may result in motion that stops at, but then 

travels through, a limit, potentially damaging the motion system. Miswired limits may 
prevent motion from occurring at all.

Keep limit and home switch signals and their ground connections wired 
separately from the motor driver/amplifier signal and encoder signal 
connections.

Wiring these signals near each other can cause faulty motion system operation 

due to signal noise and crosstalk.

By default, all limit and home inputs are digitally filtered and must be 
active for at least 1 ms. You can use MAX to disable digital filtering for 
limit and home inputs. Figure 5-2 shows a simplified schematic diagram of 
the circuit used by the limit and home switch inputs for input signal 
buffering and detection.