TMCM-1181 V3.0 Hardware Manual (Rev. 0.90 / 2015-JUL-10)
15
7 TMCM-1181 Operational Description
7.1 Calculation: Velocity and Acceleration vs. Microstep and
Fullstep Frequency
The values of the parameters sent to the TMC429 do not have typical motor values like rotations per
second as velocity. But these values can be calculated from the TMC429 parameters as shown in this
section.
PARAMETERS OF TMC429
Signal
fCLK
velocity
a_max
Description
clock-frequency
-
Range
16 MHz
0… 2047
0… 2047
maximum acceleration
divider for the velocity. The higher the value is, the less is
pulse_div the maximum velocity
default value = 0
divider for the acceleration. The higher the value is, the
ramp_div less is the maximum acceleration
0… 13
0… 13
default value = 0
0… 8 (a value of 7 or 8 is
internally mapped to 6 by the
TMC429)
Usrs
microstep-resolution (microsteps per fullstep = 2usrs
)
Table 7.1 TMC429 velocity parameters
The microstep-frequency of the stepper motor is calculated with
fCLK [Hz]⋅ velocity
usf[Hz] =
with usf: microstep-frequency
2pulse _ div ⋅ 2048 ⋅32
To calculate the fullstep-frequency from the microstep-frequency, the microstep-frequency must be
divided by the number of microsteps per fullstep.
usf[Hz]
2usrs
fsf[Hz] =
with fsf: fullstep-frequency
The change in the pulse rate per time unit (pulse frequency change per second – the acceleration a) is
given by
fCLK 2 ⋅ amax
2pulse _ div+ramp _ div+29
a =
This results in acceleration in fullsteps of:
a
2usrs
af =
with af: acceleration in fullsteps
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