TMC4330A Datasheet | Document Revision 1.01 • 2017-JAN-12
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Selecting the
Input Direction
Polarity
DIRIN polarity can be assigned. Per default, the negative direction is indicated by
DIRIN = 0.
In order to change this polarity:
Action:
Set pol_dir_in = 1 (GENERAL_CONF register 0x00).
Result:
A negative input direction is assigned by DIRIN = 1.
If an external step is not congruent with an internal step, the GEAR_RATIO register
0x12 must be set accordingly. This signed parameter consists of eight bit digits and
24 bits decimal places.
Description of
Electronic
Gearing
With every external step the assigned GEAR_RATIO value is added to an internal
accumulation register. As soon as an overflow occurs, an internal step is generated
and the remainder will be kept for the next external step.
Any absolute gearing value between 2-24 and 127 is possible.
NOTE:
Gearing ratios beyond 1 generate a burst of steps at the STPOUT pin.
A negative gearing factor GEAR_RATIO < 0 inverts the interpretation of the input
direction which is determined by DIRIN and pol_dir_in.
It is possible to use the internal ramp generator in combination with the external S/D
interface.
Indirect
External Control
In this case, the external step impulses transferred via STPIN and DIRIN cannot
influence the internal XACTUAL counter directly. Instead, the XTARGET register is
altered by 1 or -1 with every GEAR_RATIO accumulation register overflow.
NOTE:
Whether XTARGET is increased or decreased is determined similarly to the direct
electronic gearing control. The accumulation register overflow direction indicates
the target alteration. Respectively, the accumulation direction is determined by
the GEAR_RATIO sign, by pol_dir_in, and by DIRIN.
Consecutive input steps must occur with a distance of minimum 64 clock cycles.
i
This feature allows a synchronized motion of different positioning ramps for
different TMC4330A chips with differently configured ramps.
In order to select indirect external control, do as follows:
Action:
Set sdin_mode ≠ b’00 according to the required external control option.
Set sd_indirect_control = 1 (GENERAL_CONF register 0x00).
Result:
As soon as an external step is generated, XTARGET is increased or decreased,
according to the accumulation direction.
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