TMC2100 DATASHEET (Rev. 1.07 / 2017-MAY-15)
31
11.2 Changing Resolution
The TMC2100 includes an internal microstep table with 1024 sine wave entries to control the motor
coil currents. The 1024 entries correspond to one electrical revolution or four fullsteps. The microstep
resolution setting determines the step width taken within the table. Depending on the DIR input, the
microstep counter is increased (DIR=0) or decreased (DIR=1) with each STEP pulse by the step width.
The microstep resolution determines the increment respectively the decrement. At maximum
resolution, the sequencer advances one step for each step pulse. At half resolution, it advances two
steps. Increment is up to 256 steps for fullstepping. The sequencer has special provision to allow
seamless switching between different microstep rates at any time. When switching to a lower
microstep resolution, it calculates the nearest step within the target resolution and reads the current
vector at that position. This behavior especially is important for low resolutions like fullstep and
halfstep, because any failure in the step sequence would lead to asymmetrical run when comparing a
motor running clockwise and counterclockwise.
EXAMPLES:
Fullstep:
Cycles through table positions: 128, 384, 640 and 896 (45°, 135°, 225° and 315° electrical
position, both coils on at identical current). The coil current in each position
corresponds to the RMS-Value (0.71 * amplitude). Step size is 256 (90° electrical)
Half step:
The first table position is 64 (22.5° electrical), Step size is 128 (45° steps)
Quarter step: The first table position is 32 (90°/8=11.25° electrical), Step size is 64 (22.5° steps)
This way equidistant steps result and they are identical in both rotation directions. Some older drivers
also use zero current (table entry 0, 0°) as well as full current (90°) within the step tables. This kind of
stepping is avoided because it provides less torque and has a worse power dissipation in driver and
motor.
Step position
table position
64
current coil A
38.3%
current coil B
92.4%
Half step 0
Full step 0
Half step 1
Half step 2
Full step 1
Half step 3
Half step 4
Full step 2
Half step 5
Half step 6
Full step 3
Half step 7
128
192
320
384
448
576
640
704
832
896
960
70.7%
92.4%
92.4%
70.7%
38.3%
-38.3%
-70.7%
-92.4%
-92.4%
-70.7%
-38.3%
70.7%
38.3%
-38.3%
-70.7%
-92.4%
-92.4%
-70.7%
-38.3%
38.3%
70.7%
92.4%
SETTING THE MICROSTEP RESOLUTION FOR STEP INPUT BY CFG1 AND CFG2
CFG2
GND
GND
CFG1
GND
VCC_IO
open
GND
VCC_IO
open
GND
VCC_IO
open
Microsteps
1 (Fullstep)
2 (Halfstep)
2 (Halfstep)
4 (Quarterstep)
16 µsteps
4 (Quarterstep)
16 µsteps
4 (Quarterstep)
16 µsteps
Interpolation
N
N
Y, to 256 µsteps
N
N
Y, to 256 µsteps
Y, to 256 µsteps
Y, to 256 µsteps
Y, to 256 µsteps
Chopper Mode
spreadCycle
GND
VCC_IO
VCC_IO
VCC_IO
open
open
open
stealthChop
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
