TMC428 ETC-unknow, TMC428 Datasheet - Page 32

• Manufacturer Part Number: TMC428
• Description: Intelligent Triple Stepper Motor Controller With Serial Peripheral Interfaces
• Manufacturer: ETC-unknow

TMC428 DATA SHEET (V. 1.00 / February 12, 2001)
The micro step unit (including sequencer) provides the full set of control signals for three stepper motor
driver chips. A subset out of these control signals is selected by the stepper motor driver datagram
configuration, which is stored within the first 32 addresses– but up to 64 values –of the on-chip RAM (see
Table 12, page 30). The stepper motor drivers are organized in a daisy chain. So the addressing of the
stepper motor driver chips within the daisy chain is by its position.
As mentioned before, the TMC428 sends datagrams to the stepper motor driver chain on demand. To
guarantee the integrity of each datagram send to the stepper motor driver chain, the status of all primary
control signals are buffered internally before sending. Afterwards, the transmission starts with selection of
the buffered primary control signals of the first motor (smda=%00) by reading the first primary signal
code word (even data word at on-chip RAM address %00000) from on-chip configuration RAM area. The
primary signal codes select the primary signals provided for the first stepper motor. The first stepper motor
is addressed until the NxM (next motor) bit is read from on-chip configuration RAM. The stepper motor
driver address is incremented with each NxM=’1’ if the current stepper motor driver address is below the
parameter lsmd (last stepper motor driver). If the stepper motor driver address is equivalent to the lsmd
parameter, a NxM=’1’ indicates the completion of the transmission. With that, the stepper motor driver
address counter of the serial interface is reinitialized to %00 and the unit waits for the next transmission
request.
So, the order of primary signal codes in the on-chip RAM configuration area determines the order of
datagram bits for the stepper motor driver chain, whereas the prefixed NxM bit determines the stepper
motor driver positions. If no NxM bit with a value of ‘1’ is stored within the on-chip RAM, the TMC428 will
send endless. So, the on-chip RAM has to be configured first. After power-on reset, the registers of the
TMC428 are initialized, so that no transmission of datagrams to the stepper motor driver chain is required.
Access to on-chip RAM is always possible, also during transmission of datagrams to the driver chain.
Initialization of on-chip-RAM by µC after power-on
All registers are initialized by the automatic power-on reset. The registers are initialized, that stepper
motors are at rest. The on-chip RAM is not initialized by the power-on reset. Writing to registers may
involve action of the stepper motor units initiated by the TMC428 resulting in sending datagrams to the
stepper motor driver chain. Those datagrams have a random power-on configuration of the on-chip-RAM.
So, before writing any motion control register– respectively position or velocity –the on-chip RAM must be
initialized first.
An Example of a Stepper Motor Driver Datagram Configuration
The following example demonstrates, how to configure the datagram and shows what has to be stored
within the on-chip RAM to represent the desired configuration. In the example a driver chain of three
stepper motor drivers is proposed. The first stepper motor driver has a serial interface of 12 bits length,
the second driver has a length of 8 bits, and the last driver has a length of 10 bits (see Table 14). The
corresponding content of the configuration on-chip RAM is outlined in Table 15. The datagrams, to be
send from the micro controller to the TMC428, to store that configuration are outlined in Table 16.
Copyright © 2000, TRINAMIC Microchips GmbH
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