Datasheet

TMC429 DATASHEET (v. 1.07 / 2012-AUG-01) 30

Important Hint: Changing pulse_div in VELOCITY_MODE or in HOLD_MODE might force an internal

micro step (with micro step resolution defined by usrs) depending on the actual micro step position.

This is the same for the TMC429. This behavior can be observed especially when the motor is at rest

in VELOCITY_MODE or in HOLD_MODE. In RAMP_MODE this does not occur. So, pulse_div should

only be changed in RAMP_MODE.

9.15 dx_ref_tolerance (IDX=%1101)

The switches processed via the inputs REF1, REF2, REF3 can be used as stop switches for automatic

motion limiting and as reference switches defining a reference position for the stepper motor. To allow

the motor to drive near the reference point, it is possible to exclude a motion range of steps from the

stop switch function. The parameter dx_ref_tolerance disables automatic stopping by a switch around

the origin (see Figure 9-4, page 26). To use the dx_ref_tolerance fare from the origin, the actual

position has to be suitable adapted, e.g. to use it for a left side reference switch. Additionally, the

parameter dx_ref_tolerance affects interrupt conditions as described before (section 9.13, page 27).

9.16 x_latched (IDX=%1110)

This read-only register stores the actual position read from the register x_actual if the reference switch

state changes. The reference switch is defined by the bit REF_RnL of the configuration register lp &

ref_conf & ramp_mode. Writing a dummy value to the (read-only) register x_latched initializes the

position storage mechanism. Then the actual position is saved with the next rising edge or falling edge

signal of the reference switch depending on the actual motion direction of the stepper motor. The

actual position is latched when the switch defined as the reference switch by the REF_RnL bit changes

(see Table 9-4: Reference switch configuration bits (ref_conf), page 26). The status bit lp signals, if

latching of a position is pending. An event at the reference switch associated to the actual motion

direction takes effect only during motion (when v_actual  0).

9.17 Unused Address (IDX=%1111) – TMC428 vs. TMC429

This register address (IDX=%1111) within each stepper motor register block {smda=%00, %01, %10}

is unused for the TMC428. Writing to this register has no effect for the TMC428. For the TMC428 this

Reading this register gives back the actu for the TMC428.

9.17.1 ustep_count_429 (IDX=%1111)

For the TMC429, this read write register named ustep_count_429 holds the actual micro step pointer.

This register is intended for applications where the motion controller part is completely switched off for

power saving modes where the motor needs to be at the same position as during power off after re-

switching the power on.