Rainbow Electronics DS1629 - Manual (Page 7)

DS1629
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OPERATION-Alarms
The DS1629 features an open-drain alarm output with a user-definable active state (factory default is
active low). By programming the configuration register, the user also defines the event, if any, would
generate an alarm condition. The four possibilities are:
•
Temperature alarm only
•
Time alarm only
•
Either temperature or time alarm
•
Alarm disabled (power–up default)
Refer to the “OPERATION-Configuration” section for programming protocol.
If the user chooses the alarm mode under which a thermal or time event generates an alarm condition, it is
possible that either or both are generating the alarm. There are status bits in the configuration register
(TAF, CAF) that define the current state of each alarm. In this way, the master can determine which event
generated the alarm. If both events (thermal and time) are in an alarm state, the ALRM output will remain
active until both are cleared. ALRM is the logical OR of the TAF and CAF flags if the device is
configured for either to trigger the ALRM output. Figure 3 illustrates a possible scenario with this alarm
mode. Refer to the “Thermometer Alarm” and “Clock Alarm” sections on how respective alarms are
cleared.
DS1629 ALARM TRANSFER FUNCTION Figure 3