AMIS-30621 LIN Micro-stepping Motor Driver
Data Sheet
R2VBAT
A resistor is connected between VBAT and HW2. Every 1024μs SBOT is closed a current is sensed, the output of the I Æ R converter is
low and the HW2_Cmp output is high. Assuming the previous state was floating, the internal LOGIC will interpret this as a change of
state and the new state will be high. (See Table 17). The next time SBOT is closed the same conditions are observed. The previous state
was high, so based on Table 17 the new state remains unchanged. This high state will be interpreted as HW2 address = 1.
OPEN
In case the HW2 connection is lost (broken wire, bad contact in connector) the next time SBOT is closed this will be sensed. There will be
no current, the output of the corresponding I Æ R converter is high and the HW2_Cmp will be low. The previous state was high. Based
on Table 17 one can see that the state changes to float. This will trigger a motion to secure position. See also Electrical Transient
Conduction Along Supply Lines.
R2GND
If a resistor is connected between HW2 and the GND, a current is sensed every 1024μs whet STOP is closed. The output of the top I Æ
R converter is low and as a result the HW2_Cmp output switches to high. Again based on the stated diagram in Table 1 one can see
that the state will change to low. This low state will be interpreted as HW2 address = 0.
14.1.5. External Switch SWI
Figure 13 illustrates that the SWI comparator is almost identical to HW2. The major difference is in the limited number of states. Only
open or closed is recognised leading to respectively ESW = 0 and ESW = 1.
SPASS_T
IÎR
State
DriveHS
Closed
SWI
STOP
LOGIC
SBOT
Open
DriveLS
"R"-Comp
1
2
3
IÎR
SPASS_B
Rth
COMP
32 μs Debouncer
1 = R2GND
2 = R2VBAT
3 = OPEN
SWI_Cmp
Figure 13: Simplified Schematic Diagram of the SWI Comparator
Figure 15 shows a change in state is always synchronised with DriveHS or DriveLS. The same synchronisation is valid for updating the
internal position register. This means that after every current pulse (or closing of STOP or SBOT) the state of position switch together with
the corresponding position is memorized.
Using the GetActualPos commands reads back the ActPos register and the status of ESW. In this way the master node may get
synchronous information about the state of the switch together with the position of the motor. See Figure 14.
AMI Semiconductor – Sept. 2007, Rev 1.5
20
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