User Manual

TMCM-1140 Hardware Manual (Rev. 1.01 / 2012-JUL-27) 21
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8 TMCM-1140 Operational Description
8.1 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
Description
Range
f
CLK
clock-frequency
16 MHz
velocity
-
0… 2047
a_max
maximum acceleration
0… 2047
pulse_div
divider for the velocity. The higher the value is, the less is
the maximum velocity
default value = 0
0… 13
ramp_div
divider for the acceleration. The higher the value is, the
less is the maximum acceleration
default value = 0
0… 13
Usrs
microstep-resolution (microsteps per fullstep = 2
usrs
)
0… 8 (a value of 7 or 8 is internally
mapped to 6 by the TMC429)
Table 8.1 TMC429 velocity parameters
MICROSTEP FREQUENCY
The microstep frequency of the stepper motor is calculated with
3220482
][
][
_



divpulse
CLK
velocityHzf
Hzusf
with usf: microstep-frequency
FULLSTEP FREQUENCY
To calculate the fullstep frequency from the microstep frequency, the microstep frequency must be
divided by the number of microsteps per fullstep.
usrs
Hzusf
Hzfsf
2
][
][ 
with fsf: fullstep-frequency
The change in the pulse rate per time unit (pulse frequency change per second – the acceleration a) is
given by
29__
max
2
2



divrampdivpulse
CLK
af
a
This results in acceleration in fullsteps of:
usrs
a
af
2

with af: acceleration in fullsteps