TMC424-PI24 Trinamic Microchips, TMC424-PI24 Datasheet - Page 26

• Manufacturer Part Number: TMC424-PI24
• Description: Economic Miniature Three Axis Microstepping Stepper Motor Controller
• Manufacturer: Trinamic Microchips

TMC428 DATASHEET (V. 2.00 / November 12, 2003)
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 22). 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 23).
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 22). 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
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 ‘0’.
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.
Figure 9-1: Example of status bit mapping for a chain of three TMC246 or TMC249
Copyright © 2000–2003 TRINAMIC Microchips GmbH
23
23
LD2
second TMC246 driver of the chain (stepper motor # 2)
22
LD1
22
21
LD0
21
20
20
1
19
19
OT
OTPW
18
18
17
17
UV
0).
OCHS
16
16
15
OLB
15
datagram_high_word
datagram_low_word
14
OLA
14
13
OCB
13
12
OCA
12
11
11
LD2
LD2
first TMC246 driver of the chain (stepper motor # 3)
last TMC246 driver of the chain (stepper motor #1)
10
10
LD1
LD1
LD0
LD0
9
9
8
8
1
1
OT
OT
7
7
OTPW
OTPW
6
6
UV
UV
5
5
OCHS
OCHS
4
4
OLB
OLB
3
3
OLA
OLA
2
2
OCB
OCB
1
1
OCA
OCA
0
0
SDI_S
26