Operation
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4.9.1.4
Fault Processing While in Pulse & Direction Signal Input Mode
In order to allow recovery from safety-related faults such as overtemperature or current foldback while operating in
pulse & direction signal input mode, an automatic recovery mode is available. While this mode is most often used when
in pulse & direction signal input mode, it may in fact be selected even when SPI communications are available.
Automatic event recovery mode is set using the
SetDriveFaultParameter
command, and may be read back using
GetDriveFaultParameter
.
While in automatic recovery mode the
Enable
signal is used to request that the Atlas automatically attempt to reset a
fault condition. After the
FaultOut
signal goes active, the external controller must delay a minimum of 150 uSec, but
thereafter may request that the Atlas attempt to automatically recover by deasserting, and then asserting, the
Enable
signal. The
Enable
signal must be in the deasserted state for at least 150uSec for the request to be recognized.
When an automatic recovery request is recognized by Atlas it behaves as though the command sequence
ResetEventStatus 0
,
ClearDriveFaultStatus
and
RestoreOperatingMode
has been sent to it by the external
controller. As is the case when these commands are sent by the external controller, if the fault condition is still present
when recovery is attempted, Atlas will immediately again disable itself, and a recovery procedure must once again be
requested. If the fault has been corrected however, a recovery request will result in resumption of normal Atlas
operation.
4.9.2
SPI Pulse & Direction Mode
The SPI pulse & direction mode allows emulated pulse & direction information to be transmitted via the SPI bus.
While it is possible to use this mode in a production application, this mode is most useful during development, when
the values for various Atlas parameters are still being optimized, and full SPI communication is desired.
When placed in this mode an incremental signed move distance is specified via the SPI command protocol at each
external controller command. For example, a value of +7 specified by the external controller means the Atlas will
move the step motor position forward 7 microsteps, and a command of -3 will cause the Atlas to move the step motor
position backwards 3 microsteps.
To accommodate the
AtRest
signal, the SPI protocol incorporates a bit which is utilized by Atlas in the same manner
as the
AtRest
signal when in the hardware pulse & direction mode. See
Chapter 5, “SPI Communications”
for a
complete description of the SPI command format.
As was the case for pulse & direction signal mode, both a drive current and a holding current should be specified when
using the SPI pulse & direction mode. To accomplish this the command
SetCurrent
is used. The values set using this
commands can be read by the command
GetCurrent
.
To assist with operation in this mode it may be useful to read the current step motor position. This 32 bit quantity can
be read using the command
GetCommandedPosition
.
4.9.3
Current Control with Step Motors
Current control when driving step motors occurs using either field-oriented control or independent phase control. See
Section 4.5.3, “Field Oriented Control”
for a detailed description of field-oriented control, and see
for a detailed summary of the Atlas unit’s current loop.
Atlas® Digital Amplifier Complete Technical Reference
While in automatic recovery mode, the FaultOutMask should be set to assert the
FaultOut
signal during a current
foldback event. If not, the external controller will be unaware that Atlas is in a foldback condition, and therefore
will not know when to request an automatic recovery via the
Enable
signal.
