9

ATA6830

4575C–BCD–05/03

Power-up Sequence

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

cuted before a position command can be carried out. Figure 9 shows a timing diagram

on how the necessary sequences follow each other.

Figure 9. Necessary Commands after Power-up

The first sequence is the synchronization sequence. Its pattern (Figure 6) should be

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

are distortions on the bus it is helpful to send this sequence more than 4 times. A RC

lowpass filter at the bus pin (Figure 16) helps to reduce distortsions.

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

zero position. 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 impor-

tance of the reference run. After the reference run the circuit will switch to normal

operation. To perform a reference run during normal operation, the command has to be

sent only once. Figure 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