Data Sheet

go into the corresponding operation state as shown in the table above. If multiple conditions are
happening, the Tic will choose the first state (the highest state in the table above) that has an active
condition. If no conditions are happening, the Tic will proceed with normal operation. After the Tic
determines what operation state it is in, it performs the corresponding effects for that operation state
as listed in the table. These effects are explained in detail below.
Error handling variables
The “Operation state” variable says what operation state the Tic is currently in. The “Error status”
variable says what error conditions are currently happening: it has bits for most of the conditions in
the table above. The “Errors occurred” variable helps detect errors that only occur for a brief period
of time: it contains bits that get set whenever an error happens, and can be cleared with a command.
These variables can be read over TTL serial, I²C, or USB. For more information about these variables,
see Section 7.
Condition: Motor driver error
A motor driver error means that the the motor driver IC on the Tic drove its FAULT pin low to signal an
error condition.
When the Tic detects a motor driver error, it latches the error, meaning that the “Motor driver error”
bit in the “Error status” variable will stay set even after the motor driver stops signalling the fault
condition. By default, the Tic will clear the latched error every 0.5 s, but you can disable this behavior
by unchecking the “Automatically clear driver errors” checkbox in the Tic Control Center. The Tic will
also clear the latched error whenever it receives a “Clear driver error” command.
When the DRV8825 motor driver IC on the Tic T825 signals an error, it is either because of an over-
current or over-temperature condition. When the DRV8834 motor driver IC on the Tic T834 signals an
error, it is either due to an over-current, over-temperature, or under-voltage condition.
In response to a motor driver error, the Tic will go into the Reset state and assert the motor driver’s
reset line. In many cases, resetting the motor driver causes it to stop reporting the error. The Tic
latches the motor driver error so that it can avoid immediately going back to its previous state when
the driver stops reporting the error and causing a fast oscillation between states.
Motor driver errors are ignored during the brief time when the coil current is stabilizing because the
Tic T834 reports a motor driver error for a few milliseconds after coming out of its Reset state. The Tic
needs to ignore that error so it can successfully enable the motor the driver and not go back into the
Reset state.
Condition: Low VIN
The “Low VIN” error indicates that the voltage on VIN has dropped well below the minimum operating
Tic Stepper Motor Controller User’s Guide © 2001–2018 Pololu Corporation
5. Details Page 69 of 150