Data Sheet

5. Details
5.1. Motion parameters
This section explains the Tic settings and variables that directly control the motion of the stepper
motor.
Position
The Tic represents stepper motor positions in units of microsteps, which are also called pulses. The
number of microsteps that correspond to one full step is determined by the “step mode” setting.
By default, an increasing position corresponds to taking steps forward through the motor driver’s
current indexer table, so the amount of current flowing from B1 to B2 lags behind the amount of current
flowing from A1 to A2. The “invert motor direction” setting flips this correspondence.
Positions are stored as 32-bit signed integers, so they have a range of −2,147,483,648 to
+2,147,483,647 (−0x8000 0000 to +0x7FFF FFFF).
With high speeds or long system run times, it is possible for the Tic’s 32-bit “current position” variable
to overflow. If the Tic moves at its fastest speed (50,000 kHz) in one direction for approximately
12 hours, that would correspond to more than 2,147,483,647 microsteps. The Tic considers position
+2,147,483,647 to be adjacent to position −2,147,483,648, and if you command it to go from one
position to another, it will use the direction that gets it to the target position in the least number of
steps, even if that involves letting the current position variable wrap around. Position overflow should
not cause any issues for the Tic, but it could be important to consider it if you are writing software to
control the Tic and dealing with positions.
Speed
The Tic represents speeds in units of microsteps (or pulses) per 10,000 seconds. For example, a
speed of 200,000 corresponds to 20 microsteps per second. A speed is a non-negative integer that
expresses how fast a stepper motor could move, but does not express direction.
The allowed range of speeds is 0 to 500,000,000 (50,000 pulses per second, or 50 kHz), but speeds
from 1 to 6 will behave the same as speed 0 (see below).
Low speed considerations
Speeds from 1 to 6 will behave the same as a speed of 0 (the Tic will never take a step when the
speed is so low because its step planning algorithm cannot keep track of times that long). Therefore,
the minimum speed that the Tic can actually achieve is 7 steps per 10,000 seconds, or one step every
23 minutes.
It is important to note that the Tic only allows integer (whole number) speeds. So if your stepper motor
Tic Stepper Motor Controller User’s Guide © 2001–2018 Pololu Corporation
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