POWERSTEP01 datasheet(55/92 Pages) STMICROELECTRONICS

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powerSTEP01

Programming manual

11.1.8

MIN_SPEED

The MIN_SPEED register contains the following parameters:

The MIN_SPEED parameter contains the speed profile minimum speed. Its value is

expressed in step/tick and to convert it in step/s the following formula can be used:

Equation 8

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

The available range is from 0 to 976.3 step/s with a resolution of 0.238 step/s.

When the LSPD_OPT bit is set high, low speed optimization feature is enabled (voltage

mode driving only) and the MIN_SPEED value indicates the speed threshold below which

the compensation works. In this case the minimum speed of the speed profile is set to zero.

Any attempt to write the register when the motor is running causes the CMD_ERROR flag to

rise.

11.1.9

FS_SPD

The FS_SPD register contains the following parameters:

The FS_SPD threshold speed value over which the step mode is automatically switched to

full-step two-phase on. Its value is expressed in step/tick (format unsigned fixed point 0.18)

and to convert it in step/s the following formula can be used:

Equation 9

If FS_SPD value is set to hFF (max.) the system always works in Microstepping mode

(SPEED must go over the threshold to switch to Full-step mode). Setting FS_SPD to zero

does not have the same effect as setting the step mode to full-step two-phase on: the zero

FS_SPD value is equivalent to a speed threshold of about 7.63 step/s.

The available range is from 7.63 to 15625 step/s with a resolution of 15.25 step/s.

The BOOST_MODE bit sets the amplitude of the voltage squarewave during the full-step

operation (see Section on page 24).

Table 14. MIN_SPEED register

Bit 12

Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

LSPD_OPT

MIN_SPEED

step/s

 MIN_SPEED 2

–



tick

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

Table 15. FS_SPD register

Bit 10

Bit 9

Bit 8

Bit 7 Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

BOOST_MODE

FS_SPD

step/s



FS_SPD 0.5

 2

–



tick

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