Specifications

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3401 Manual
Point I/O Stepper Module
Revision 2.0
Chapter 4: Command Mode Operations
The following is a description of the various commands that the module accepts and the operations that it
will perform while in Command Mode. When switching from Configuration Mode to Command Mode,
the position will be invalid and the Current Position will be zero.
Absolute/Relative Move
The current position must to be valid in order to perform an ABSOLUTE MOVE. A HOME or PRESET
operation will have to be performed before the position becomes valid. The distance moved, that is the
number of pulses issued by the 3401, is equal to the difference between the Target Position and the
Current Position. For example, if the Current Position is 5000, and the Target Position is 7500, than the
unit will output 2500 pulses. After the Absolute Move has been completed, the Current Position will be
7500. The direction of motion of an Absolute Move is determined by the relationship between the
Current Position and Target Position. If the Target Position > Current Position, than CW motion will
occur. If the Target Position < Current Position, than CCW motion will occur.
The current position does not have to be valid to perform a RELATIVE MOVE. The Target Position
defines the distance, in number of pulses, to travel relative to the Current Position. For example, if the
Current Position is 5000 and the Target Position is 7500, than the unit will output 7500 pulses. After the
Relative Move has been completed, the Current Position will be 12,500. The direction of motion of a
Relative Move is selected by the sign of the Target Position. A positive Target Position will generate a
CW move while a negative Target Position will generate a CCW move.
The ABSOLUTE or RELATIVE MOVE operations can produce two different velocity profiles.
Normally the move operations start at the Starting Speed, accelerate to the Programmed speed at the
defined acceleration rate, continue at the Programmed speed until it is time to decelerate back to the
Starting Speed, and Stop. This generates a trapezoidal velocity profile.
However, if the move operation does not reach the Programmed speed by the time the deceleration is to
begin, the move is decelerated to the Starting Speed and Stopped. In this way a triangular velocity profile
is generated.
If the move operation runs to completion without error, the MOVE COMPLETE FLAG is set. If an error
does occur, the MOVE COMPLETE FLAG will not be set, and an error flag will be set.