L9942_V01 datasheet(22/40 Pages) STMICROELECTRONICS

22 / 40 page

Functional description of the logic with SPI

L9942

22/40

Doc ID 11778 Rev 7

Note:

Due to this safety functionality a daisy chaining of SPI is not possible. Instead, a parallel

operation of the SPI bus by controlling the CSN signal of the connected ICs is

recommended.

4.6

Serial data out (DO)

The data output driver is activated by a logical low level at the CSN input and will go from

high impedance to a low or high level depending on the status bit 0 (fault condition). The first

rising edge of the CLK input after a high to low transition of the CSN pin will transfer the

content of the selected status register into the data out shift register. Each subsequent

falling edge of the CLK will shift the next bit out.

4.7

Serial clock (CLK)

The CLK input is used to synchronize the input and output serial bit streams. The data input

(DI) is sampled at the rising edge of the CLK and the data output (DO) will change with the

falling edge of the CLK signal.

4.8

Data register

The device has eight data registers. The first three bits (bit 0 ... bit 2) at the DI-input are used

to select one of the input registers. All bits are first shifted into an input shift register. After

the rising edge of CSN the contents of the input shift register will be written to the selected

Input Data Register only if a frame of exact 16 data bits are detected. The selected register

will be transferred to DO during the current communication frame.

Figure 9.

SPI and registers

CLK_ADR

D10

D11

DIR

AI0

AI1

AI2

AI3

AI4

BI0

BI1

BI2

BI3

BI4

DAC Phase B

DAC Phase A

Phase

D12

Phase Counter

Current Profile 0

Current Profile 1

OVW

Openload

LSA1

HSA1

LSA2

HSA2

LSB1

LSB2

HSB1

HSB2

Overcurrent

OV(W)

CSN

CLK

INT_2MHz

SPI-

Controll

POR

Slew Rate

Step Mode

SR0

SR1

ST1

ST0

DAC_Scale

DC1

DC2

Temperature

VS Monitor

SEL_ERROR

SPI2REG

TSD

RREF

Error

CLR7

CLR6

Read-Only

DC0

Read Only

PWM

Freq

Current Profile 8

Read-Only

Current Profile 2

Current Profile 3

NPWM

PWM Counter

Current Profile 4

Current Profile 5

Current Profile 6

Current Profile 7

Decay Mode

DM0

DM1

DM2

SST

Test only

PWM

PWM Counter

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