L6470PD datasheet(27/70 Pages) STMICROELECTRONICS

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L6470

Functional description

Doc ID16737 Rev 5

27/70

The GoUntil command makes the motor run at the constant target speed until the SW input

is forced low (falling edge). When this event occurs, one of the following actions can be

performed:

●

The ABS_POS register is set to zero (home position) and the motor decelerates to zero

speed (as a SoftStop command)

●

The ABS_POS register value is stored in the MARK register and the motor decelerates

to zero speed (as a SoftStop command).

If the SW_MODE bit of the CONFIG register is set to ‘0’, the motor does not decelerate but

it immediately stops (as a HardStop command).

The ReleaseSW command makes the motor run at the programmed minimum speed until

the SW input is forced high (rising edge). When this event occurs, one of the following

actions can be performed:

●

The ABS_POS register is set to zero (home position) and the motor immediately stops

(as a HardStop command)

●

The ABS_POS register value is stored in the MARK register and the motor immediately

stops (as a HardStop command).

If the programmed minimum speed is less than 5 step/s, the motor is driven at 5 step/s.

6.8

Internal oscillator and oscillator driver

The control logic clock can be supplied by the internal 16-MHz oscillator, an external

oscillator (crystal or ceramic resonator) or a direct clock signal.

These working modes can be selected by EXT_CLK and OSC_SEL parameters in the

CONFIG register (see Table 23).

At power-up the device starts using the internal oscillator and provides a 2-MHz clock signal

on the OSCOUT pin.

Attention:

In any case, before changing clock source configuration, a

hardware reset is mandatory. Switching to different clock

configurations during operation may cause unexpected

behavior.

6.8.1

Internal oscillator

In this mode the internal oscillator is activated and OSCIN is unused. If the OSCOUT clock

source is enabled, the OSCOUT pin provides a 2, 4, 8 or 16-MHz clock signal (according to

OSC_SEL value); it is otherwise unused (see Figure 12).

6.8.2

External clock source

Two types of external clock source can be selected: crystal/ceramic resonator or direct clock

source. Four programmable clock frequencies are available for each external clock source:

8, 16, 24 and 32 MHz.

When an external crystal/resonator is selected, the OSCIN and OSCOUT pins are used to

drive the crystal/resonator (see Figure 12). The crystal/resonator and load capacitors (CL)

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