AMIS-30622 Datasheet, PDF (18/42 Pages) AMI SEMICONDUCTOR – I2C Microstepping Motordriver

AMIS-30622
9.2.1.3. External switch and HW pin
Pin SWI and hardwired address pin HW (see § 9.2.4.3 Physical Address) will alternatively attempt to source and
sink a current in/from the external switch (see application schematic) to test whether it is ON or OFF. This
current is set around 10mA when a 1kΩ external series resistor is used.
source current
sink current
Tsw_on
Tsw/2
Tsw
Tsw_on
This can be represented by the following time diagram (The timings are given in § 6).
If the switch is detected ON (closed), then the flag <ESW> is raised. The status of this flag can be read by the
application via a GetActualPos or a GetFullStatus1 reading frame. At the falling edge of every current
pulse (at around 1kHz), the stepper-motor actual position is refreshed (register ActPos, see § 9.2.2.9), so that
the master node may get synchronous information about the state of the switch together with the position of the
motor. The position is then given with an accuracy of ± 1 half-step (or micro-step, depending of the programmed
stepping mode). The block diagram below shows how this function is implemented for HW.
Vbb
A-m
convert I -> R
Source
HW
Sink
R threshold
+
Source
-
Sink
HW_CMP
A-m
GND
convert I -> R
With the following truth table:
State
Sink
Source New State HWHi
address = "1"
Float
1
Float
1
Float
0
Float
0
HWLo
1
HWLo
1
HWLo
0
HWLo
0
HWHi
1
HWHi
1
HWHi
0
HWHi
0
0
Float
HWLo
address = "0"
0
HWHi
1
Float
1
HWLo
0
HWLo
0
HWHi
1
Float
1
HWLo
0
Float
0
HWHi note that e.g. if HW is connected to GND, LS-
1
HWHi part will report "float" while HS-part will report
1
HWLo ^{"low resistance detected"}
Note
If HW is detected to be floating, motion to the secure position is performed.
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