Operation
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Atlas® Digital Amplifier Complete Technical Reference
4
The instantaneous status of the overvoltage threshold comparison can be read using the command
GetDriveStatus
.
4.8.4
Undervoltage Fault
Atlas also provides the capability to sense undervoltage conditions. To set the programmable threshold the command
SetDriveFaultParameters
is used. This value is compared to the value read from the drive DC bus, and if the value
read is less than the programmed threshold, an undervoltage fault occurs. See
Section 3.11.1, “Atlas Settings Defaults
for a list of undervoltage-related limits and defaults.
Threshold units, recovery procedure, and all other aspects of this feature are the same as for overvoltage sense except
that the bit status location in the Drive Fault Status register is different. Just as for overvoltage conditions, it is the
user's responsibility to determine the seriousness of, and appropriate response to, an undervoltage condition.
4.8.5
Watchdog Timeout
Atlas provides a programmable watchdog timer that can detect an unexpected lack of activity from the external
controller. Typically, such a condition is due to an SPI communication problem or an external controller malfunction.
Particularly when the external controller is used to provide higher level velocity or position control, a watchdog
timeout may therefore represent a very serious condition.
To effect the watchdog function Atlas monitors the amount of time between successive valid SPI torque or voltage
commands from the external controller. If the amount of time between commands exceeds the programmed
watchdog timer, the watchdog fault is triggered.
To set the watchdog timeout value the
SetDriveFaultParameter
command is used. To read the value set using this
command,
GetDriveFaultParameters
is used. The watchdog time value is in units of 51.2 uSec. For example a value
of 100 indicates a timeout interval of 5,120 uSec or 5.12 mSecs. A value of zero (0) means the watchdog is disabled.
A watchdog timeout fault will cause the following events to occur:
• The current loop and power stage modules are disabled, thereby halting further motor output.
• The Drive Fault Status register records a watchdog timeout fault condition.
• The Event Status register records a drive exception condition.
To recover from this condition the user should determine the nature of the fault using the
GetDriveFaultStatus
command. In most cases it is desirable to power down Atlas to correct the condition.
If the condition is resolved but Atlas is not power cycled, the following sequence should be used to restore the drive
to normal operation:
• Clear the fault condition using the
ClearDriveFaultStatus
command.
• Clear the drive exception bit of the Event Status word using the
ResetEventStatus
command. It is not
possible to re-enable the current loop or the power stage module if the drive exception bit is still active.
• Re-enable the current loop and power stage modules using the
RestoreOperatingMode
command.
Overvoltage faults indicate that a serious safety condition has occurred. It is the responsibility of the user to op-
erate Atlas within safe limits.
