L6470PD datasheet(42/70 Pages) STMICROELECTRONICS

42 / 70 page

Programming manual

L6470

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Doc ID16737 Rev 5

9.1.3

MARK

The MARK register contains an absolute position called MARK according to the selected

step mode; the stored value unit is equal to the selected step mode (full, half, quarter, etc.).

It is in 2's complement format and it ranges from -221 to +221-1.

9.1.4

SPEED

The SPEED register contains the current motor speed, expressed in step/tick (format

unsigned fixed point 0.28).

In order to convert the SPEED value in step/s, the following formula can be used:

Equation 4

where SPEED is the integer number stored in the register and tick is 250 ns.

The available range is from 0 to 15625 step/s with a resolution of 0.015 step/s.

Note:

The range effectively available to the user is limited by the MAX_SPEED parameter.

Any attempt to write the register causes the command to be ignored and the

NOTPERF_CMD flag to rise (see Section 9.1.22).

9.1.5

ACC

The ACC register contains the speed profile acceleration expressed in step/tick2 (format

unsigned fixed point 0.40).

In order to convert ACC value in step/s2, the following formula can be used:

Equation 5

where ACC is the integer number stored in the register and tick is 250 ns.

The available range is from 14.55 to 59590 step/s2 with a resolution of 14.55 step/s2.

When the ACC value is set to 0xFFF, the device works in infinite acceleration mode.

Any attempt to write to the register when the motor is running causes the command to be

ignored and the NOTPERF_CMD flag to rise (see Section 9.1.22).

9.1.6

DEC

The DEC register contains the speed profile deceleration expressed in step/tick2 (format

unsigned fixed point 0.40).

In order to convert DEC value in step/s2, the following formula can be used:

Equation 6

step/s

[]

SPEED

–

⋅

tick

----------------------------------------

step/s

[]

ACC

–

⋅

tick

-------------------------------

step/s

[]

DEC

–

⋅

tick

-------------------------------

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