L9779WD datasheet(80/170 Pages) STMICROELECTRONICS

80 / 170 page

Functional description

L9779WD

80/170

DocID027452 Rev 5

Stepper counter

In order to keep trace of the stepper movement in L9779WD a 10-bit register is available

(5 bits in the STEP_CNT_H and 5 bits in the STEP_CNT_L)

The value of this register after the power-up is 512 and:



with DIR=1 the value is increased by one for each step of the motor



with DIR=0 the value is decreased by one for each step of the motor.

When the counter reaches the max or min value it remains at that value unless the direction

is inverted.

In the STEP_CNT_H and STEP_CNT_L registers there are two bits used to check if the

content of the register is referred to the same motor step.

The stepper counter is reset by power-on reset and software reset.

Figure 49. Stepper counter diagram

Driver parallel configuration

Low side drivers can be connected in parallel to increase the current driving capability. High

side drivers behave similarly.

Configurations are set by CONFIG_REG7 and CONFIG_REG10.

6.13.2

Diagnosis of configurable power stages (CPS)

All CPS have fault diagnostic functions:



Short-circuit to battery voltage: (SCB) can be detected if switches are turned on



Short-circuit to ground:

(SCG) can be detected if switches are turned off



Open load:

(OL) can be detected if switches are turned off



Over temperature:

(OT) will be detected with the general thermal

warning(OT2)

Diagnosis is different for configuration as full-bridges or as single power stages. The faults

are coded in different way and are stored in diagnostic registers.

In each configuration the registers can be read via MSC. With the beginning of each read

cycle the registers are cleared automatically.

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