Datasheet

TMC429 DATASHEET (v. 1.07 / 2012-AUG-01) 38
Copyright © 2010-2012, TRINAMIC Motion Control GmbH & Co. KG
A1
SCK_S
SDO_S
SDI_S
nSCS_S
REF2 REF3
REF1
TEST GND
SDI_C
nSCS_C
SCK_C
SDO_C
CLK
V5V33
TMC428 / TMC429
A0
A < MUX
B
C
D
B1
B0
C1
C0
D1
D0
SEL1/ /0
/EN
REF1_LEFT REF1_RIGHT
REF2_LEFT
REF2_RIGHT
REF3_LEFT
REF3_RIGHT
+VCC
74HC157
Figure 10-7: Reference switch multiplexing with 74HC157 (refmux=1)
refmux
mot1r
motor 1
motor 2
motor 3
left switch
right switch
left switch
right switch
left switch
right switch
0
0
REF1
%
REF2
%
REF3
%
0
1
REF1
REF3
REF2
%
%
%
1
0
REF1_LEFT
REF1_RIGHT
REF2_LEFT
REF2_RIGHT
REF3_LEFT
REF3_RIGHT
1
1
REF1_LEFT
REF1_RIGHT
REF2_LEFT
REF2_RIGHT
REF3_LEFT
REF3_RIGHT
Table 10-5: Association of reference inputs depending on configuration bits refmux & mot1r
If continuous_update  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 10-7). So, the continuous_update 
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 Figure 10-7). For
the two variants TMC429-PI24 and TMC429-LI, the reference switch multiplexing also works for
csCommonIndividualseparate driver selection signals (nSCS_S, nSCS2, nSCS3) if
the signal nSCS_S is connected to the multiplexer 74HC157 according to Figure 10-10.
If reference switch multiplexing is enabled, mot1r is ignored. With refmux 
the reference switch inputs REF1, REF2, REF3 depends on the setting of the configuration bit mot1r.
The power-on default value of mot1r       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 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 10-5). After power-on-reset, per default refmux=0
and mot1r=0 selects the single reference switch configuration outlined in Figure 10-4, where each
reference switch input (REF1, REF2, REF3) is assigned individually to one each stepper motor as the
left reference switch.