AMIS-30521 Datasheet, PDF (15/28 Pages) AMI SEMICONDUCTOR – Micro-stepping Motor Driver

AMIS−30521, NCV70521
I_Y
I_Y
Start = 0 Step 1
Step 2
Step 3
I_X
Start = 0
Step 1
Start = 0
Step 2 _IX
I_Y
Step 1
I_X
1/4th Micro Step
SM[2:0] = 011
Step 3 _{Step 3}
Step 2
Uncompensated Half Step
SM[2:0] = 101
Full Step
SM[2:0] = 110
Figure 9. Translator Table: Circular and Square
PC20071116.1
Direction
The direction of rotation is selected by means of following
combination of the DIR input pin and the SPI−controlled
direction bit <DIRCTRL> as illustrated in Table 12.
NXT Input
Changes on the NXT input will move the motor current
one step up/down in the translator table (even when the
motor is disabled). Depending on the NXT−polarity bit
<NXTP> (see Table 12), the next step is initiated either on
the rising edge or the falling edge of the NXT input.
Translator Position
The translator position can be read in SPI Status Register
3. This is a 7−bit number equivalent to the 1/32th micro−step
from Table 10: “Circular Translator Table” above. The
translator position is updated immediately following a NXT
trigger.
Synchronization of Step Mode and NXT Input
When step mode is re−programmed to another resolution,
(Figure 11), this is put in effect immediately upon the first
arriving “NXT” input. If the micro−stepping resolution is
increased, the coil currents will be regulated to the nearest
micro−step, according to the fixed grid of the increased
resolution. If however the micro−stepping resolution is
decreased, then it is possible to introduce an offset (or phase
shift) in the micro−step translator table.
If the step resolution is decreased at a translator table
position that is shared both by the old and new resolution
setting, then the offset is zero and micro−stepping proceeds
according to the translator table.
If the translator position is not shared both by the old and
new resolution setting, then the micro−stepping proceeds
with an offset relative to the translator table (See Figure 11
right hand side).
NXT
Update
Translator Position
Update
Translator Position
Figure 10. Translator Position Timing Diagram
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