DocID025240 Rev 2

9/25

AN4355

Motion engine control

25

If a GoTo command is requested when the motor is running, the minimum path algorithm

also considers the steps required to reverse the direction (see Figure 6).

Figure 6. Minimum path algorithm when motor is running

The GoTo and GoTo_DIR can only be executed when no other commands are under

execution.

Change the target position of the on-the-fly command

If a Run command is sent to the device during the execution of a GoTo command, it aborts

the previous command. This effect can be used to change the target position of the motion

engine on-the-fly.

Following the suggested sequence of operations:

1.

Read the current motor speed (SPEED register) and direction (DIR bit in the STATUS

register).

2.

Send a Run command setting the target speed and direction equal to the values

obtained at point 1.

3.

Wait for the execution command monitoring the BUSY pin or the BUSY flag in the

STATUS register.

4.

Send the new positioning command.

This operation could introduce a small error in the generation of the speed profile. If the

target position is changed a high number of times (tracking position) the error increases and

anomalous behaviors could occur.

0

h200000

>

then forward direction is used.

h3FFFFF

h1FFFFF

h000001

Current position

Zero speed position

(where the motor will stop if it starts decelerating)

Target position

Motor is running

in forward direction

Forward direction path

Forward direction path

Reverse direction path

Reverse direction path

AM16592v1