TMC260 and TMC261 DATASHEET (Rev. 2.05 / 2012-NOV-05)
28
7.3 Changing Resolution
The application may need to change the microstepping resolution to get the best performance from
the motor. For example, high-resolution microstepping may be used for precision operations on a
workpiece, and then fullstepping may be used for maximum torque at maximum velocity to advance
to the next workpiece. When changing to coarse resolutions like fullstepping or halfstepping,
switching should occur at or near positions that correspond to steps in the lower resolution, as
shown in Table 7.1.
Step Position
MSTEP Value
Coil A Current Coil B Current
Half step 0
Full step 0
Half step 1
Full step 1
Half step 2
Full step 2
Half step 3
Full step 3
0
0%
70.7%
100%
70.7%
0%
-70.7%
-100%
-70.7%
100%
70.7%
0%
-70.7%
-100%
-70.7%
0%
128
256
384
512
640
768
896
70.7%
Table 7.1 Optimum positions for changing to halfstep and fullstep resolution
7.4 microPlyer Step Interpolator
For each active edge on STEP, microPlyer produces 16 microsteps at 256x resolution, as shown in
Figure 7.3. microPlyer is enabled by setting the INTPOL bit in the DRVCTRL register. It supports input
at 16x resolution, which it transforms into 256x resolution. The step rate for each 16 microsteps is
determined by measuring the time interval of the previous step period and dividing it into 16 equal
parts. The maximum time between two microsteps corresponds to 220 (roughly one million system
clock cycles), for an even distribution of 1/256 microsteps. At 16MHz system clock frequency, this
results in a minimum step input frequency of 16Hz for microPlyer operation (one fullstep per second).
A lower step rate causes the STST bit to be set, which indicates a standstill event. At that frequency,
ꢖꢗꢖꢘꢙꢚꢇꢛꢜꢝꢛꢞꢇꢟꢠꢙꢡꢢꢙꢣꢛꢗ
microsteps occur at a rate of
ꢧ ꢨꢩꢪꢫꢬ ꢌ ꢨꢭꢭ.
ꢥꢦ
ꢤ
microPlyer only works well with a stable STEP frequency. Do not use the DEDGE option if the
STEP signal does not have a 50% duty cycle.
STEP
interpolated
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
16 17 18 19 20 21 22 23 3233343536373839404142434445464748495051525354555657585960616263646566
microstep
motor
angle
2^20 tCLK
STANDSTILL
(STST) active
Figure 7.3 microPlyer microstep interpolation with rising STEP frequency.
www.trinamic.com
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
