L9942 datasheet(23/40 Pages) STMICROELECTRONICS

23 / 40 page

L9942

SPI - control and status registers

Doc ID 11778 Rev 7

23/40

SPI - control and status registers

5.1

The meaning of the different bits is as follows:

Table 14.

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 > 4 µs

010

Mixed decay, fast decay until TMD > 8 µs

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 > 4 µs

110

Auto decay, fast decay until TMD > 8 µs

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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