TMC428_06 Datasheet, PDF (9/58 Pages) List of Unclassifed Manufacturers – Intelligent Triple Stepper Motor Controller with Serial Peripheral Interfaces

TMC428 DATASHEET (v. 2.02 / April 26^th, 2006)
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A complete serial datagram frame has a fixed length of 32 bit. While the data transmission from the
microcontroller to the TMC428 is idle, the low active serial chip select input nSCS_C and also the serial
data clock signal SCK_C are set to high. While the signal nSCS_C is high, the TMC428 assigns the
status of the internal low active interrupt signal named nINT to the serial data output SDO_C (see
Figure 6-1). The serial data input SDI_C of the TMC428 has to be driven by the microcontroller.
Important Hint: In contrast to most other SPI^TM compatible devices, the SDO_C signal of the TMC428
is always driven. So, it will never be high impedance ‘Z’. If high impedance is required for the SDO_C
connected to the microcontroller, it can simply be realized using a single gate 74HCT1G125.
nSCS_C
SDI_C
SCK_C
SDOZ_C
REF1 REF2 REF3
nSCS_S
nSCS_C
SDI_C
SCK_C
TMC428
SDO_S
SCK_S
SDO_C _CLK
V33
V5 TEST GND ^SDI_S
74HCT1G125
Figure 4 : Making the TMC428 SDO_C output high impedance with single gate 74HCT1G125
The signal nSCS_C has to be high for at least three clock cycles before starting a datagram
transmission. To initiate a transmission, the signal nSCS_C has to be set to low. Three clock cycles
later the serial data clock may go low. The most significant bit (MSB) of a 32 bit wide datagram comes
first and the least significant bit (LSB) is transmitted as the last one. A data transmission is finished by
setting nSCS_C high three or more CLK cycles after the last rising SCK_C slope. So, nSCS_C and
SCK_C change in opposite order from low to high at the end of a data transmission as these signals
change from high to low at the beginning. The timing of the serial microcontroller interface is outlined in
Figure 6-1.
6.3 Serial Peripheral Interface to Stepper Motor Driver Chain
The timing of the serial stepper motor interface is similar to that of the microcontroller interface. It
directly connects to SPI^TM smart power stepper motor drivers. The SPI^TM datagram is configurable
individually for each stepper motor driver chip of the daisy chain. It is simply configurable by sending a
fixed sequence of datagrams to the TMC428 to initialize it after power-up. Once initialized, the TMC428
autonomously generates the datagrams for the stepper motor driver daisy chain without any additional
interventions of the microcontroller.
The SPI^TM datagram for each stepper motor driver is composed of so called primary signal bits
provided by the micro step unit of the TMC428 individually for each stepper motor. Each primary signal
bit is represented by a five bit code word called primary signal code. The order of primary signal bits
forming the SPI^TM datagrams for the stepper motor driver daisy chain is defined by the order of primary
signal code words in the configuration RAM area.
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