NPA Commander Online Manual

The slowdown switch (SD) input indicates a point to begin deceleration. If the slowdown switch inputs are active when the motor is operating at HSPD speed and this signal is triggered, the motor will start to decelerate. 

The 2-bit SDE[axis] command enables the SD inputs and sets the latching function. By default, SDEX=0 disables the X-axis SD inputs.  The inputs can be enabled without a latch function using SDEX=1, or enabled with a latch function SDEX=3.

Table 2-1  SDE command

The SDC[axis] command determines the specific operation of the SD input. By default, SDC[axis]=0 sets the operation, when triggered, to decelerate the motor to LSPD without stopping.  When SDC[axis]=1, the operation is set to decelerate and stop when the SD input is triggered. 

Table 2-2  SDC command

Triggering the SD input when SDC=1 will set the SD stop flag, MST[axis](bit17).  The SD stop flag will not prevent further motion, but can only be cleared by using the CLR[axis] command in ASCII mode or the ECLEAR[axis] command in standalone mode.

The SD input, when triggered, will cause the motor to slowdown regardless of the direction of travel.

The figure below shows an example of a setup using the slowdown inputs.  These inputs are mainly used in homing operations.  In this case the axis would move at HSPD, trigger the slowdown input, allowing the motor to decelerate to LSPD, before it triggers the home input.

Other uses for the slowdown input are placing SD limits at each end of travel just before the end limits.  This allows for two options.  The slowdown inputs function as a soft limit (SDC=1) that decelerates and stops the motion, allowing the end limits to operate as emergency hard end limits.  Or they can just allow the motor to decelerate (SDC=0) to LSPD before triggering the end limits.  The polarity of the slowdown inputs is set with the POL[axis](Bit6).

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