Motion engine control

AN4355

6/25

DocID025240 Rev 2

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Motion engine control

The L648x devices integrate a motion engine providing a full set of commands. The motion

engine generates the step sequence according to the programmed speed profile and the

requested command.

The speed profile represents the operation boundaries, defined by the acceleration,

deceleration, maximum and minimum speed, which should be respected to ensure the

proper functioning of the application.

The devices allow all the parameters to be set independently:



Acceleration and deceleration values range from 14.55 up to 59590 steps/s2. The

device can also be set to use an infinite acceleration and deceleration value; in this

case, both the acceleration and deceleration phases are totally skipped.



Maximum speed value ranges from 15.25 steps/s up to 15610 step/s.



Minimum speed value ranges from 0 up to 976 steps/s.

The acceleration, deceleration and minimum speed parameters can be modified when the

motor is stopped only. The maximum speed can be also changed when the motor is

running, but the new value is only considered at next command execution.

The commands supported by the motion engine are listed in Table 1.

Table 1. Command list

Name

Length

(bytes)

Description

Notes

Move

4 (including 3

of arguments)

Performing the target number of microsteps

as per requested direction.

Can be executed when the motor is

stopped only.

GoTo

4 (including 3

of arguments)

Reaching the absolute target position

(ABS_POS register) using the shortest path.

Not accepted while another command

is under execution.

GoTo_DIR

4 (including 3

of arguments)

Reaching the absolute target position

(ABS_POS register) running as per requested

direction.

Not accepted while another command

is under execution.

GoHome

1

Reaching the home position (all zeroes) using

the shortest path.

Not accepted while another command

is under execution.

GoMark

1

Reaching the position stored into the MARK

register using the shortest path.

Not accepted while another command

is under execution.

Run

4 (including 3

of arguments)

Reaching the target speed in the requested

direction.

Always accepted and immediately

executed (if present, the previous

command is aborted)

StepClock

1

Switching the device in step-clock mode

imposing the direction.

Can be executed when the motor is

stopped only.

GoUntil

4 (including 3

of arguments)

Reaching the speed target in the requested

direction and stopping when SW input is

forced low (falling edge).

Always accepted and immediately

executed (if present, the previous

command is aborted)

ReleaseSW

1

Running the motor at low speed in the

requested direction and stopping when SW

input is forced high (rising edge).

Always accepted and immediately

executed (if present, the previous

command is aborted)