Rainbow Electronics DS1678 - Manual (Page 15)

DS1678
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locations 0000h and 0001h, overwriting the original data. Likewise, subsequent samples will increment
through the event log registers, overwriting their data.
The event 0 elapsed time from last event bytes will have the elapsed time since the last event in the event
log memory. This is to allow the user to recover the information prior to the rollover. At the start of a
mission, the value in these 2 bytes will be all zeros since there was no previous event from which to have
an elapsed time.
If RO is set to a 0, no further event logs will be written to the event log memory after all event log
memory registers have been filled. Events, however, will continue to be recognized and the Event Count
register will be incremented for each event. Likewise, the RTC alarm flag will also continue to function.
TR1, TR0 - Trigger Select [1,0] – This bit selects the edge(s) that will activate the INT pin to cause an
event to be logged. An event can be triggered one of three ways depending on the settings of the TRx bits
in the control register. With TR0 bit set to a 1 and TR1 bit set to a 0, the
INT signal will be activated on
the falling edge of the input signal. With the TR0 bit set to a 0 and the TR1 bit set to a 1, the INT pin will
be activated on the rising edge of the input signal.
With both TR0 and TR1 bits set to 1, the INT pin will be activated by both the rising and falling edges to
allow for the measurement of on/off type events and their durations. If TR0 and TR1 are both set to 0,
nothing will happen when the
INT pin is toggled and a mission will not start. This is an illegal state and
the mission will not start without a valid value in the TRx bits prior to attempting to start the mission.
TRIGGER SELECT BITS Table 3
TR1 TR0 EDGE(S) USED TO TRIGGER AN EVENT
0 0 Nothing, Illegal State
0 1 Falling Edge
1 0 Rising Edge
1 1 Both Rising and Falling Edges
COE - Clock Oscillator Enable – This bit allows the clock oscillator to be shut off to save power. The
RTC will no longer keep time when the oscillator is shut off, but the information stored in the device
memory will be maintained. An event log mission can not start with COE set to zero and the RTC must
be reset to the correct value after the oscillator is restarted and prior to starting a mission in order to
obtain good data. A clear memory can also not be executed without the oscillator running. When V
CC
>
V
BAT
, the oscillator will automatically start, no matter what the value in the COE bit to allow proper
communications. This is a way to preserve the data longer in battery mode once a mission has been
completed in order to increase the battery life and thus the data integrity lifetime.
STATUS REGISTER
MSB LSB
0 MEM CLR MIP CM LOBAT ROF 0 ALMF
MEM CLR - Memory Cleared – This bit indicates that the event log memory, event count, and start
time stamp registers are all cleared to zero. MEM CLR is cleared to zero when an event log mission is
started (i.e., MIP = 1).