8902–A

3-PHASE BRUSHLESS DC

MOTOR CONTROLLER/DRIVER

Serial Port. The serial port functions to write various operational

and diagnostic modes to the A8902CLBA. The serial port DATA IN is

enabled/disabled by the CHIP SELECT terminal. When CHIP SE-

LECT is high the serial port is disabled and the chip is not affected by

changes in data at the DATA IN or CLOCK terminals.

To write data to the serial port, the CLOCK terminal should be low

prior to the CHIP SELECT terminal going low. Once CHIP SELECT

goes low, information on the DATA IN terminal is read into the shift

register on the positive-going transition of the CLOCK. There are 24

bits in the serial input port.

Data written into the serial port is latched and becomes active

upon the low-to-high transition of the CHIP SELECT terminal at the

end of the write cycle. D0 will be the last bit written to the serial port.

SERIAL PORT BIT DEFINITIONS

D0- Sleep/Run Mode; LOW = Sleep, HIGH = Run

This bit allows the device to be powered down when not in use.

D1- Step Mode; LOW = Normal Operation, HIGH = Step Only

When in the step-only mode the back-EMF commutation circuitry

is disabled and the power outputs are commutated by the start-

up oscillator. This mode is intended for device and system

testing.

D2- Brake; LOW = Run, HIGH = Brake.

D3 and D4 - These two bits set the output current limit:

D3

D4

Current Limit

0

0

1.2 A

0

1

1 A

1

0

600 mA

1

1

250 mA

desired motor speed.

Bit Number

Count Number

D5

16

D6

32

D7

64

D8

128

D9

256

D10

512

D11

1 024

D12

2 048

D13

4 096

D14

8 192

D15

16 384

D16

32 768

D17

65 536

D18

131 072

D19-Speed-control mode switch;

LOW = internal once-around speed signal,

HIGH = external sector data.

D20 and D21-These bits program the number

counter:

D20

D21

Motor Poles

00

8

01

–

10

16

11

12

D22 and D23-Controls the multiplexer for

DATA OUT:

D22

D23

DATA OUT

0

0

TACH (once around or sector)

0

1

Thermal Shutdown

1

0

SYNC

1

1

FCOM

Reset. The RESET terminal when pulled

low clears all serial port bits, including the D0

latch, which puts the A8902CLBA in the sleep

mode.