ST L6470H User Manual

L6470 Functional description
Doc ID 16737 Rev 2 21/64
When motor speed is greater than a programmable full step speed threshold, the L6470
switches automatically to full-step mode; the driving mode returns to microstepping when
motor speed decrease below the full step speed threshold. Full step speed threshold is set
through the FS_SPD register (see Section 9.1.9).
6.5 Absolute position counter
An internal 22 bit register (ABS_POS) takes memory of motor motion according to the
selected step mode; the stored value unit is equal to the selected step mode (full, half,
quarter, etc.). The position range is from -2
21
to +2
21
-1 (µ)steps (see Section 9.1.1).
6.6 Programmable speed profiles
The user can easily program a customized speed profile defining independently
acceleration, deceleration, maximum and minimum speed values by ACC, DEC,
MAX_SPEED and MIN_SPEED registers respectively (see Section 9.1.5, 9.1.6, 9.1.7 and
9.1.8).
When a command is sent to the device, the integrated logic generates the microstep
frequency profile that performs a motor motion compliant to speed profile boundaries.
All acceleration parameters are expressed in step/tick
2
and all speed parameters are
expressed in step/tick; the unit of measure does not depend on selected step mode.
Acceleration and deceleration parameters range from 2
-40
to (2
12
-2)•2
-40
step/tick
2
(equivalent to 14.55 to 59590 step/s
2
).
Minimum speed parameter ranges from 0 to (2
12
-
1
)•2
-24
step/tick (equivalent to 0 to 976.3
step/s).
Maximum speed parameter ranges from 2
-18
to (2
10
-1)• 2
-18
step/tick (equivalent to 15.25 to
15610 step/s).
6.6.1 Infinite acceleration/deceleration mode
When ACC register value is set to max (0xFFF), system works in “infinite acceleration
mode”: acceleration and deceleration phases are totally skipped as shown in Figure 6.
It is not possible to skip the acceleration or deceleration phase independently.
Figure 6. Speed profile in infinite acceleration/deceleration mode
30%%$
)ND
EXINGMODE #ONSTANTSPEEDMODE
TIME
0ROGRAMMEDNUMBEROFMICROSTEPS
TIME
!-6
0ROGRAMMED
MAXIMUM
SPEED

ST L6470H Specifications

General

Brand	ST
Model	L6470H
Category	Computer Hardware
Language	English