TMC428 ETC-unknow, TMC428 Datasheet - Page 15

• 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)
Register Description
The registers contain binary coded numbers. Some are unsigned, positive numbers, some are signed
numbers in two’s complement, and some are just bit vectors or bit vectors of single flags.
x_target (IDX=%0000)
This register holds the current target position in units of full steps respectively micro steps. The unit of the
target position depends on the setting of the associated micro step resolution register usrs. If the
difference x_target - x_actual is not zero then the TMC428 moves the stepper motor that the difference
becomes zero. Both, target position x_target and current position x_actual (usually not necessary) may
be altered on the fly. To move from one position to another, the ramp generator of TMC428
automatically generates ramp profiles (step pulses with defined frequencies) in consideration of velocity
limits v_min and v_max and acceleration limit a_max.
Note: The registers x_target, x_actual, v_min, v_max, and a_max are initialized with zero after power
up. Thus, no step pulses are generated because motion is prohibited. Setting a_max to zero during
motion of the stepper motor results in the inability of the stepper motor to stop, because it cannot change
its velocity.
x_actual (IDX=%0001)
The current position of each stepper motor is available by read out of the registers called x_actual. The
actual position can be over written by the micro controller. This feature is for reference switch calibration
under control of the micro controller. If a reference switch position has been determined, the actual
position is set to zero at the reference switch position.
v_min (IDX=%0010)
This register holds the absolute value of the velocity where the stepper motor can be stopped abruptly. It
should be set greater than zero. This value allows to reach the target position faster because the stepper
motor is not slowed down below v_min before the target is reached. Also consider, that due to the finite
numerical representation of integral relations, the target position can not be reached exactly, if the
calculated velocity is less than one. So, setting v_min to one assures reaching each target position exactly.
The unit of velocity parameters (v_max, v_target, and v_actual) is steps per time unit. The time unit is
defined by the parameter pulse_div. The pulse frequencies in unit steps per second depends on the clock
frequency of the clock signal at pin CLK of the TMC428.
Figure 7 - Velocity ramp parameters and velocity profiles
Copyright © 2000, TRINAMIC Microchips GmbH
TRINAMIC
M I C R O C H I P S
v_max
v_min
v(t)
t
0
acceleration
t
01
t
v
1
constant velocity
t
2
deceleration
t
3
t
4
t
5
acceleration
t
56
t
v
6
deceleration
t
7
t
8
t
15
15