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set the activation state of the limit switches refer to the command CN, configure, in the Command
Reference.
When a forward or reverse limit switch is activated, the current application program that is running
will be interrupted and the controller will automatically jump to the #LIMSWI subroutine if one exists.
This is a subroutine which the user can include in any motion control program and is useful for
executing specific instructions upon activation of a limit switch.
After a limit switch has been activated, further motion in the direction of the limit switch will not be
possible until the logic state of the switch returns back to an inactive state. This usually involves
physically opening the tripped switch. Any attempt at further motion before the logic state has been
reset will result in the following error: "022 - Begin not possible due to limit switch" error.
The operands, _LFx and _LRx, return the state of the forward and reverse limit switches, respectively
(x represents the axis, X,Y,Z, or W). The value of the operand is either a '0' or '1' corresponding to
the logic state of the limit switch, active or inactive, respectively. If the limit switches are configured
for active low, no connection or a 5V input will be read as a '0', while grounding the switch will return
a '1'. If the limit switches are configured for active high, the reading will be inverted and no
connection or a 5V input will be read as a '1', while grounding the switch will return a '0'.
Using a terminal program, the state of a limit switch can be printed to the screen with the command,
MG _LFx or MG _LRx. This prints the value of the limit switch operands for the 'x' axis. The logic
state of the limit switches can also be interrogated with the TS command. For more details on TS,
_LFx, _LRx, or MG see the Command Reference.
Home Switch Input
Homing inputs are designed to provide mechanical reference points for a motion control application.
A transition in the state of a Home input alerts the controller that a particular reference point has been
reached by a moving part in the motion control system. A reference point can be a point in space or an
encoder index pulse.
The Home input detects any transition in the state of the switch and changes between logic states 0 and
1, corresponding to either 0V or 5V depending on the configuration set by the user (CN command).
The CN command can be used to customize the homing routine to the user's application.
There are three homing routines supported by the CDS-3310: Find Edge (FE), Find Index (FI), and
Standard Home (HM).
The Find Edge routine is initiated by the command sequence: FEX <return>, BGX <return> (where X
could be any axis on the controller, X,Y,Z, or W). The Find Edge routine will cause the motor to
accelerate, then slew at constant speed until a transition is detected in the logic state of the Home input.
The direction of the FE motion is dependent on the state of the home switch. Refer to the CN
command to set the correspondence between the Home Input voltage and motion direction. The motor
will decelerate to a stop when a transition is seen on the input. The acceleration rate, deceleration rate
and slew speed are specified by the user, prior to the movement, using the commands AC, DC, and SP.
It is recommended that a high deceleration value be used so the motor will decelerate rapidly after
sensing the Home switch.
The Find Index routine is initiated by the command sequence: FIX <return>, BGX <return> (where X
could be any axis on the controller, X,Y,Z, or W). Find Index will cause the motor to accelerate to
the user-defined slew speed (SP) at a rate specified by the user with the AC command and slew until
the controller senses a change in the index pulse signal from low to high. The motor then decelerates
to a stop at the rate previously specified by the user with the DC command. Although Find Index is an
option for homing, it is not dependent upon a transition in the logic state of the Home input, but
instead is dependent upon a transition in the level of the index pulse signal.
The Standard Homing routine is initiated by the sequence of commands HMX <return>, BGX
<return> (where X could be any axis on the controller, X,Y,Z, or W). Standard Homing is a
combination of Find Edge and Find Index homing. Initiating the standard homing routine will cause
i
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Chapter 3 Connecting I/O
CDS-3310
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