L6472PD datasheet(57/69 Pages) STMICROELECTRONICS

57 / 69 page

L6472

Programming manual

Doc ID 022729 Rev 1

57/69

Any attempt to read an inexistent register (wrong address value) causes the command to be

ignored and WRONG_CMD flag to rise at the end of command byte as if an unknown

command code is sent.

9.2.5

Run (DIR, SPD)

The Run command produces a motion at SPD speed; the direction is selected by the DIR

bit: '1' forward or '0' reverse. The SPD value is expressed in step/tick (format unsigned fixed

point 0.28) which is the same format as the SPEED register (see Section 9.1.4).

Note:

The SPD value should be lower than MAX_SPEED and greater than MIN_SPEED

otherwise the Run command is executed at MAX_SPEED or MIN_SPEED respectively.

This command keeps the BUSY flag low until the target speed is reached.

This command can be given anytime and is immediately executed.

9.2.6

StepClock (DIR)

The StepClock command switches the device in step-clock mode (see Section 6.7.5) and

imposes the forward (DIR = '1') or reverse (DIR = '0') direction.

When the device is in step-clock mode the SCK_MOD flag in the STATUS register is raised

and the motor is always considered stopped (see Section 6.7.5 and 9.1.18).

The device exits from step-clock mode when a constant speed, absolute positioning or

motion command is sent through SPI. Motion direction is imposed by the respective

StepClock command argument and can by changed by a new StepClock command without

exiting step-clock mode.

Events that cause bridges to be forced into high-impedance state (overtemperature,

overcurrent, etc.) do not cause the device to leave step-clock mode. StepClock command

does not force the BUSY flag low. This command can only be given when the motor is

stopped. If a motion is in progress the motor should be stopped and it is then possible to

send a StepClock command.

Any attempt to perform a StepClock command when the motor is running causes the

command to be ignored and the NOTPERF_CMD flag to rise (see Section 9.1.19).

Table 37.

Run command structure

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

DIR

From host

SPD (Byte 2)

From host

SPD (Byte 1)

From host

SPD (Byte 0)

From host

Table 38.

StepClock command structure

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

DIR

From host

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