8

ATA6830

4575C–BCD–05/03

Bus Commands

There are different commands for controlling the stepping motor. Table 1 shows a list of

all implemented commands and their meanings. The first command, the synchronization

sequence, is described above. The second group of commands are the reference com-

mands. A reference run command causes the stepping motor to make an initial run. It is

used to establish a defined start position for the following position commands. The way

the reference run is executed will be described later. There are two reference run com-

mands. The difference is the turn direction of the stepping motor. This makes the circuit

more flexible for different applications. The turn direction is coded in the 4 identifier bits.

The last class of commands are the position commands. Every new position will be sent

as an absolute value. This makes the transmission more safe in terms of losing a posi-

tion command. The next received command tells the stepping motor the right position

again. For the position data there are 10 bits available (D0 to D9).

The maximum possible step count to be coded with 10 bit is 1024. Though position com-

mands up to 1024 will be executed, it´s prohibited to use values higher than 698, as this

is the step count of the reference run. For details see chapter “Reference Run”.

There are 4 new position commands. They differ in the identifier and in the modus bits.

The identifier fixes the turn direction. For test purposes there are new position com-

mands with a different mode. In this mode the stepping motor works with a reduced coil

current. This may be used for end tests in the production of the application.

Any command with modus or identifier different to the first reference run will be ignored.

Thus it is also not possible to change modus or identifier by performing a second refer-

ence run.

Table 1. Bus Commands

Bus Command

High Byte

Low Byte

Data

Mode

Identifier

Data

76

5

4

321076

543210

Synchronization

1

0

1

0

101010

101010

Reference run (extend)

00

0

0

100100

000000

Reference run (retract)

00

0

0

011000

000000

New position (0 = full extension)

D8

D9

0

0

1001

D0

D1

D2

D3

D4

D5

D6

D7

New position (0 = full retraction)

D8

D9

0

0

0110

D0

D1

D2

D3

D4

D5

D6

D7

New position

(testmode, 0 = full extension)

D8

D9

1

1

1001

D0

D1

D2

D3

D4

D5

D6

D7

New position

(testmode, 0 = full retraction)

D8

D9

1

1

0110

D0

D1

D2

D3

D4

D5

D6

D7