9

4575D–BCD–09/05

ATA6830

3.6

Power-up Sequence

After power-up the circuit has to be synchronized and a reference run has to be executed before

a position command can be carried out. Figure 3-7 shows a timing diagram on how the neces-

sary sequences follow each other.

Figure 3-7.

Necessary Commands after Power-up

The first sequence is the synchronization sequence. Its pattern (Figure 3-4 on page 7) should be

sent at least 4 times to be sure that the following commands will be recognized. If there are dis-

tortions on the bus it is helpful to send this sequence more than 4 times. A RC lowpass filter at

the bus pin (Figure 8-1 on page 20) helps to reduce distortions.

After synchronization the stepping motor has to make the reference run to initialize its zero posi-

tion. The first reference run will only be executed if the circuit recognizes this command three

times in series. This function is implemented contributing to the importance of the reference run.

After the reference run the circuit will switch to normal operation. To perform a reference run dur-

ing normal operation, the command has to be sent only once. Figure 3-8 on page 10 shows the

state diagram for the implemented sequence processor.

1

2

4

1

SYNCHRONIZATION

SEQUENCE

2

10

REFERENCE RUN

SEQUENCE

MESSAGE

FRAME

POWER

UP

POSITION 1

POSITION 2