L9942 datasheet(21/37 Pages) STMICROELECTRONICS

21 / 37 page

L9942

5 SPI - Control and Status Registers

21/37

SPI - Control and Status Registers

5.1

Control Register 0

The meaning of the different bits is as follows:

Bit

Phase Counter

Decay Mode

Slew Rate

Step Mode

DIR

Access

r w

Reset

Name

DM2

DM1

DM0

SR1

SR0

ST1

ST0

DIR

This bit controls direction of motor movement. DIR=1 clockwise DIR=0 counter clockwise.

ST1 ST0

This bits controls step mode of motor movement (

Figure 3).

Micro-stepping

Mini-stepping

Half-stepping

Full-stepping

SR1 SR0

This bit controls slew rate of bridge switches. See also parameter

Table 13

DM2 DM1 DM0

This bits controls decay mode of output current (

Figure 3).

000

Slow decay

001

Mixed decay, fast decay until TMD > 4us

010

Mixed decay, fast decay until TMD > 8us

011

Mixed decay, fast decay until

current undershoot Tmc =TFT +TCC

100

Auto decay, fast decay without delay time

Auto decay uses mixed decay automatically

to reduce current for next step if required (

see

Figure 3 down right).

101

Auto decay, fast decay until TMD > 4us

110

Auto decay, fast decay until TMD > 8us

111

Auto decay, fast decay until current

undershoot Tmc

P4 P3 P2 P1 P0

This bits control position of motor, e.g. 00000 step angle

is 0°, 01111 step angle is 180°..

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