TMC428_06 Datasheet, PDF (7/58 Pages) List of Unclassifed Manufacturers – Intelligent Triple Stepper Motor Controller with Serial Peripheral Interfaces

TMC428 DATASHEET (v. 2.02 / April 26^th, 2006)
7
5 Functional Description and Block Diagram
From the software point of view, the TMC428 provides a set of registers of different units and on-chip
RAM (see Figure 5-1), accessed via the serial µC interface in an uniform way. The serial interface uses
just a simple protocol with fixed length datagrams for read and write access. The serial interface to the
stepper motor driver chain has to be configured by an initialization sequence which writes the
configuration into the on-chip RAM. Once configured the serial driver interface works autonomously.
The internal multiple port RAM controller of the TMC428 takes care of access scheduling. So, the user
may read and write registers and on-chip RAM at any time. The registers hold global configuration
parameters and the motion parameters. The on-chip RAM stores the configuration of the serial driver
interface and the micro step table.
The ramp generator monitors the motion parameters stored in its registers and calculates velocity
profiles controlling the pulse generator. The pulse generator then generates step pulses taking into
account user defined motion parameter limits. The serial driver interface sends datagrams to the
stepper motor driver chain whenever a step pulse comes. The micro step unit (including sequencer)
processes step pulses from the pulse generator– representing micro steps, half steps, or full steps
depending on the selected step resolution –and makes the results available to the serial driver
interface. The ramp generator also interfaces the reference switch inputs. Unused reference switches
have to be connected to ground. A pull-down resistor is necessary at the SDI_S input of the TMC428
for those serial peripheral interface stepper motor drivers that set their serial data output to high
impedance ‘Z’ while inactive.
The interrupt controller continuously watches reference switches and ramp generator conditions and
generates an interrupt if required. To save pins, the interrupt signal is multiplexed to the SDO_C signal.
This output becomes the low active interrupt signal called nINT while nSCS_C is high (see Figure 6-1,
page 8). So, if the microcontroller disables the interrupt during access to the TMC428 and enables the
interrupt otherwise, the multiplexed interrupt output of the TMC428 behaves like a dedicated interrupt
output. For polling, the TMC428 sends the status of the interrupt signal to the microcontroller with each
datagram.
To drive a stepper motor to a new target position, one just has to write the target position into the
associated register by sending a datagram to the TMC428. To run a stepper motor with a target
velocity, one just has to write the velocity into the register assigned to the stepper motor.
nSCS_C
SCK_C
SDI_C
SDO_C
serial µC interface
interrupt
controller
ramp generator
&
pulse generator
CLK
TEST
Figure 5-1: TMC428 functional block diagram
micro step unit
( including
sequencer )
serial driver interface
multiple
ported RAM
power-on
reset
voltage
regulator
GND
[nSCS2]
[nSCS3]
nSCS_S
SCK_S
SDO_S
SDI_S
10K
V5
V33
470nF
Copyright © 2004-2006, TRINAMIC Motion Control GmbH & Co. KG