L7250 datasheet(11/46 Pages) STMICROELECTRONICS

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L7250

SERIAL PORT

The serial port is a bidirectional three pin interface, using SDATA, SCLK and SEN to address and communicate

with sixteen 8 bit registers in the L7250. These registers include the status register, Spindle control registers,

VCM control registers, sinewave drive registers, and test mode register. These registers are cleared to zero at

power up.

1.1 Default comunication modes setting (bit 7, Reg05H ) = 0

After the SEN falling edge, the internal state machine is waiting for the first SCLK falling edge. This means that

if the SCLK line starts from an high level the first falling edge, respecting the setup time Tefcf, is considered,

and is used to read the R/W bit. During a writing process the internal state machine must see 16 SCLK falling

edges to validate the operation. The write mode is started if the R/W bit is low on the first falling edge of SCLK.

The read mode is started if the R/W bit is high on the first falling edge of SCLK. The ID, Address, and Data are

all then subsequently read by the L7250 on the falling edges of SCLK. (See Figure 1)

The microcontroller has to read the data on the falling edge of the SCLK signal. After the hold time (Tedh) the

data line switches to the next data without a tri-state phase.During a read mode the last address bit is read by

L7250 on the eighth falling edge of SCLK. The internal state machine then turns the SDATA bit around for the

L7250 to assume control at the next SCLK rising edge (the first rising edge after the 8th SCLK falling edge).

SERIAL PORT

Voh

Logic Output voltage high

Ioh=1mA

2.7

Vol

Logic Output voltage low

Iol=1mA

0.5

Vih

Logic input high

Iih=1uA

2.2

Vil

Logic input low

Iil=-1uA

0.5

Iih

Logic high input current

Internal Pulldown Resistor

Vin = 3.3V

µA

Iil

Logic low input current

-1.00

µA

ELECTRICAL CHARACTERISTCS (continued)

POWER SUPPLY [VCC5 & VCV] VCC5 = 5V ±10%, VCV = 12V ±10%. Tamb = 25°C (unless otherwise specified)

Symbol

Parameter

Test Condition

Min.

Typ.

Max.

Unit

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