TMC428_06 Datasheet, PDF(33/58 Page) List of Unclassifed Manufacturers – Intelligent Triple Stepper Motor Controller with Serial Peripheral Interfaces

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TMC428_06 Datasheet, PDF (33/58 Pages) List of Unclassifed Manufacturers – Intelligent Triple Stepper Motor Controller with Serial Peripheral Interfaces

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TMC428 DATASHEET (v. 2.02 / April 26th, 2006)

refmux

mot1r

motor 1

left switch right switch

REF1

REF3

REF1_LEFT REF1_RIGHT

RE1_LEFT REF1_RIGHT

motor 2

left switch right switch

REF2

REF2_LEFT REF2_RIGHT

motor 3

left switch right switch

REF3

REF3_LEFT REF3_RIGHT

Table 9-3: Association of reference inputs depending on configuration bits refmux & mot1r

If continuous_update is â1â, internal reference switch bits are updated periodically, even if all stepper

motors are at rest. Additionally, the chip select signal nSCS_S for the stepper motor driver chain is

also the control signal for a multiplexer in case of using the reference switch multiplexing option (see

Figure 9-5). So, the continuous_update must be set to â1â if automatic stop by reference switches is

enabled, if six multiplexed reference switches are used, and to get the states of reference switches

while all stepper motors are at rest.

The bit named refmux must be set to â1â to enable reference switch multiplexing (see Figure 9-5). For

the two variants TMC428-PI24 and TMC428-DI20, the reference switch multiplexing also works for

csCommonIndividual=â1â using three separate driver selection signals (nSCS_S, nSCS2, nSCS3) if

the signal nSCS_S is connected to the multiplexer 74HC157 according to Figure 9-8.

If reference switch multiplexing is enabled, mot1r is ignored. With refmux set to â0â, the association of

the reference switch inputs REF1, REF2, REF3 depends on the setting of the configuration bit mot1r.

The power-on default value of mot1r is â0â. With that default value, REF1 is associated to the left

reference switch of stepper motor #1, REF2 is associated to the left reference switch of stepper motor

#2, and REF3 is associated to the left reference switch of stepper motor #3.

If mot1r is set to â1â the input REF1 is also associated with the left reference switch of stepper motor

#1. REF2 is also associated to the left reference switch of stepper motor #2. But, the input REF3 is

associated to the right reference switch of stepper motor #1 and no reference switch input is

associated to stepper motor number#3 (see Figure 9-4). After power-on-reset, per default refmux=0

and mot1r=0 selects the single reference switch configuration outlined in Figure 9-3, where each

reference switch input (REF1, REF2, REF3) is assigned individually to one each stepper motor as the

left reference switch.

9.8 Triple Switch Configuration

The programmable tolerance range around the reference switch position is useful for a triple switch

configuration, as outlined in Figure 9-6. In that configuration two switches are used as automatic stop

switches, and one additional switch is used as the reference switch between the left stop switch and

the right stop switch. The left stop switch and the reference switch are wired or. After successful

reference search, programming a tolerance range into the register dx_ref_tolerance allows to disable

automatic stop within the range of the reference switch only.

left stop

switch

motor

negative direction

traveller

x'1 x'left x'2

xtraveler

reference switch

x1 x0 x2

right stop

switch

x3 xright x4

positive direction

dx_ref_tolerance

Figure 9-6: Triple switch configuration 'left stop switch - reference switch - right stop switch'

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