AMIS-30621 datasheet(13/43 Pages) AMI

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AMI Semiconductor - Rev. 1.4

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9.2.1.2 Position Initialization

After power-up or when a Vdd reset has been

acknowledged to the master, a position initialization of the

stepper-motor can be requested by the application, by use

of the RunInit command (see § 9.2.2.11). The position

initialization is performed by the position controller under

the control of the Main control block. This operation cannot

be interrupted or influenced by any further command. A

position

initialization

can

only

interrupted

by the occurrence of the conditions driving to a Motor

shutdown (see § 9.2.2.8) or by a HardStop command. On

the other hand, sending a RunInit command while a

motion is already ongoing is not recommended.

A position initialization consists of 2 successive motions, as

illustrated below.

The first motion is done with the specified Vmin and Vmax

velocities in the RunInit command, with the acceleration

(deceleration) parameter already in RAM, to a position

Pos1[15:0]

also specified in RunInit. The goal here is to

perform a motion large enough to reach a stall position

(considered to be the reference position).

Then a second motion to a position Pos2[15:0] is done at

the specified Vmin velocity in the RunInit command (no

acceleration). The purpose of this second motion is to

confirm with a low velocity the positioning of the motor at

the stall position, assuming that the stepper motor may

have bounced against the stall position. Therefore, Pos2

should only be a few half or micro steps further than Pos1,

in order to perform a displacement of at least one electrical

period.

Once the second motion is achieved, the ActPos register

(see § 0) is reset to zero, to set the reached position as the

reference position, whereas TagPos register is not

changed.

Notes

(0) The priority encoder (see § 9.2.2.12) is describing the

management of states and commands. The notes below

are to be considered illustrative.

(1) The last SetPosition(Short) command issued during

an initialization sequence will be kept in memory and

executed afterwards. This applies also for the

commands

Sleep

and

SetMotorParam

and

GotoSecurePosition

(2) Commands such as GetActualPos or GetStatus will

be executed while the position initialization is running.

This applies also for a dynamic ID assignment LIN frame

(see § 9.2.4.6.4).

(3) An initialization sequence starts by setting TagPos register

to SecPos value, provided secure position is enabled

otherwise TagPos is reset to zero.

(4) The acceleration/deceleration value applied during an

initialization sequence is the one stored in RAM before the

RunInit

command is sent. The same applies for Shaft

bit, but not for Irun, Ihold and StepMode, which can

be changed during an initialization sequence.

(5) The Pos1, Pos2, Vmax, and Vmin values programmed in

a RunInit command apply only for a this initialization

sequence. All further positioning will use the parameters

stored in RAM (programmed for instance by a former

SetMotorParam

command).

(6) Commands ResetPosition, RunInit and SoftStop

will be ignored while an initialization sequence is

ongoing, and will not be executed afterwards.

(7) A SetMotorParam command should not be sent during

an initialization sequence.

(8) If for some reason ActPos equals Pos1[15:0] at the

moment the RunInit command is issued, the circuit will

enter in deadlock state. Therefore, the application should

check the actual position by a GetPosition or a

GetFullStatus

command prior to an initialization.

Another solution may consist in programming a value out

of the stepper motor range for Pos1[15:0].

AMIS-30621 LIN Microstepping Motordriver

Data Sheet

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