TMC428_06 Datasheet, PDF(27/58 Page) List of Unclassifed Manufacturers – Intelligent Triple Stepper Motor Controller with Serial Peripheral Interfaces

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TMC428_06 Datasheet, PDF (27/58 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)

8.15 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 8-4, page 23). 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 8.13, page 24).

8.16 x_latched (IDX=%1110)

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

becomes active. 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 signal of the

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

latched if the switch defined as the reference switch by the REF_RnL bit (see Table 8-4: Reference

switch configuration bits (ref_conf), page 23). 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 â 0).

8.17 Unused Address (IDX=%1111)

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

unused. Writing to this register has no effect. However, access should be avoided, because this

address space may be used for future devices. Reading this register gives back the actual status bits

and 24 data bits set to â0â.

9 Global Parameter Registers

The registers addressed by RRS=0 with SMDA=%11 are global parameter registers. To emphasize

this difference, the JDX is used as index name instead of IDX.

9.1 datagram_low_word (JDX=%0000) & datagram_high_word (JDX=%0001)

The TMC428 stores datagrams sent back from the stepper motor driver chain with a total length of up

to 48 bits. The register datagram_low_word holds the lower 24 bits of this 48 bits and the register

datagram_high_word holds the higher 24 bits of the 48 bits. These registers together form a 48 bit

shift register, where the data from pin SDI_S are shifted left into it with each datagram bit sent to the

stepper motor driver chain via the signal SDO_S. A write to one of these read-only registers initializes

them, to update their contents with the next datagram received from the drivers chain.

datagram_high_word

LD2

LD1

LD0

OTPW

OCHS OLB

OLA

OCB

OCA

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

last TMC246 driver of the chain (stepper motor #1)

datagram_low_word

LD2

LD1

LD0

OTPW

OCHS OLB

OLA

OCB

OCA

LD2

LD1

LD0

OTPW

OCHS OLB

OLA

OCB

OCA

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

second TMC246 driver of the chain (stepper motor # 2)

first TMC246 driver of the chain (stepper motor # 3)

Figure 9-1: Example of status bit mapping for a chain of three TMC246 or TMC249

SDI_S

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