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
).
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
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
,
and
).
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
.
It is not possible to skip the acceleration or deceleration phase independently.
Figure 6.
Speed profile in infinite acceleration/deceleration mode
30%%$
)NDEXINGMODE
#ONSTANTSPEEDMODE
TIME
0ROGRAMMEDNUMBEROFMICROSTEPS
TIME
!-6
0ROGRAMMED
MAXIMUM
SPEED
