Datasheet

78M6610+PSU Data Sheet
It is also possible to set the accumulation interval based on a number of AC Voltage line cycles. If the
Line Lock (LL) Command register bit is set and AccumCyc register is non-zero then the device will
calculate, on every frequency update, a new Accum value based upon the line frequency. The formula is
as follows:
=
SampleRate
Line Frequency
 18
The computed Accum value locks the accumulation interval to the number of AC line voltage
cycles, specified by the AccumCyc line cycles regardless of the system frequency.
2.6 Zero-Crossing Detection
The 78M6610+PSU includes a zero-crossing detection feature on both AC input channels. The zero-
crossing detection allows measurements to be synchronized to the frequency of the incoming waveforms.
The time delay of the zero-crossing output versus the effective zero crossing is approximately 500 µs.
2.7 Alarms
The 78M6610+PSU includes a set of user-configurable alarms. Most alarms have a corresponding
register to store the threshold above which (in the case of “max” limits), or below which (in the case of
“min” limits) an alarm condition is generated. Such a condition does not necessarily cause an alarm. The
condition must exist for the duration of the associated hold-off time.
If the alarm condition exceeds the hold-off time, an alarm event is generated and reported in the
corresponding bit of the alarm register. The corresponding event counter is also incremented.
The alarm bit will continue to be set as long as the alarm condition persists, even if the user clears it by
accessing the AlarmReset register. However, event counters will only record one event until the next new
assertion of the alarm.
The registers AlarmMask1 and AlarmMask2 allow the user to select which alarm will be used to drive the
corresponding alarm pins (AlarmMask1 controls ACFAULT pin while AlarmMask2 controls ACCRIT pin).
For example, to select OverCurrent and Vsurge to drive the ACFAULT pin, AlarmMask1 should be set to
0x000440.
The AlarmSet register allows forcing a particular alarm in the alarm register. This function is mainly
intended for relay control and system test purposes.
The AlarmReset register allows clearing a particular alarm in the alarm register.
The AlarmSticky register allows the user to select which bits in the alarm register should remain set even
after the alarm condition no longer exists. These bits will remain set until reset by the host/user. All other
Alarms will be reset at the end of the accumulation interval unless the alarm condition remains.
Exceptions: Relay_On, Zero_Cross, and Data_Ready are not influenced by the value of the AlarmSticky
register. By default, all the bits in the AlarmSticky register are set.
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