TMCM-111-56 Manual
17
Copyright © 2006, TRINAMIC Motion Control GmbH & Co. KG
7 TMCM-111 Operational Description
7.1 Calculation: Velocity and Acceleration vs. Microstep- and
Fullstep Frequency
The values of the parameters sent to the TMC428 do not have typical motor values, like rotations per second
as velocity. But these values can be calculated from the TMC428 parameters, as shown in this document. The
parameters for the TMC428 are:
Parameter
Description
Range
f
CLK
Clock frequency
16 MHz
velocity
0..2047
a_max
Maximum acceleration
0..2047
pulse_div
Velocity pre-divider. The higher the value is, the less
is the maximum velocity.
Default value = 3
Can be changed in TMCL using SAP 154.
0..13
ramp_div
Acceleration pre-divider. The higher the value is, the
less is the maximum acceleration
default value = 7
Can be change in TMCL using SAP 153.
0..13
Usrs
Microstep resolution (microsteps per fullstep = 2
usrs
).
Can be changed in TMCL using SAP 140.
0..6
Table 7.1: TMC428 Velocity parameters
The
microstep-frequency
of the stepper motor is calculated with
32
2048
2
velocity
]
Hz
[
f
]
Hz
[
usf
div
_
pulse
CLK
⋅
⋅
⋅
=
with usf: microstep-frequency
To calculate the
fullstep-frequency
from the microstep-frequency, the microstep-frequency must be divided
by the number of microsteps per fullstep.
usrs
2
]
Hz
[
usf
]
Hz
[
fsf
=
with fsf: fullstep-frequency
The change in the pulse rate per time unit (microstep frequency change per second – the
acceleration a
) is
given by
29
div
_
ramp
div
_
pulse
max
2
CLK
2
a
f
a
+
+
⋅
=
This results in an acceleration in fullsteps of:
usrs
2
a
af
=
with af: acceleration in fullsteps
