DS1678S Maxim Integrated Products, DS1678S Datasheet - Page 11

• Manufacturer Part Number: DS1678S
• Description: IC RECORDER REALTIME EVENT 8SOIC
• Manufacturer: Maxim Integrated Products
• Type: Time Event Recorderr

Specifications of DS1678S

• Memory Size: 32B
• Time Format: HH:MM:SS (12/24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (5.3mm Width), 8-SOP, 8-SOEIAJ
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DS1678
written to the two event 0 elapsed time from last event registers, the subsequent event log will be written
to address locations 0000h and 0001h, and the address pointer will be incremented with each successive
data sample. When this rollover occurs, the roll over flag (ROF) in the control register will be set to one
to indicate that the memory has rolled over at least one time.
The second option for dealing with data overrun is to simply stop the recording of events after the event
log memory has been completely used. In other words, the DS1678 will stop recording event logs after
event 1025. More precisely, when the address pointer is incremented from 07FFh to 0000h after the last
memory byte is filled with a log, the DS1678 will stop recording events. This feature is enabled by
setting the Rollover bit to 0. The device will still continue monitoring the
pin and the event counter
INT
will continue to increment when the
pin is activated even though the event log memory has been
INT
filled.
It should be noted that during an event log mission, a time stamp for the first event is recorded, but is not
included for each subsequent event. However, the time of acquisition for any event is easily determined
by considering the start time, the value in the event counter register, ROF, and the address of the
particular data sample in the event log memory.
If no rollover has occurred in the event log memory (ROF = 0), the sample time associated with any
particular data point can be calculated by multiplying the sum of the elapsed time between the events up
to that event by one second, minute, or hour depending on which resolution is selected in the DISx bits of
the control register, and adding this elapsed time to the value in the start time stamp register.
If the rollover feature has been enabled, the user can determine if rollover has occurred by reading the
value in the events counter register or the ROF. The event counter register counts the total number of
events that have been acquired. If this value is greater than 0400h (decimal 1025) then the user knows
that rollover has occurred. If rollover has occurred, the user needs to determine how many times rollover
occurred in determining the sample time for any particular data sample. The address pointer will be
pointing to the oldest data in the event log memory and if the memory has rolled over at least one time,
the roll over flag will be set to 1.
As a safety measure, the DS1678 has been designed such that the end user cannot write to the event log
memory. This prevents the falsification of event log data by writing values to event log registers.
CLOCK, CALENDAR, AND ALARM
The time and calendar information is accessed by reading/writing the appropriate register bytes. Note
that some bits are set to zero. These bits will always read zero regardless of how they are written. The
contents of the time, calendar, and alarm registers are in the BCD format and are year 2000-compliant.
The DS1678 can run in either 12-hour or 24-hour mode. Bit 6 of the hour’s register is defined as the 12-
or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the
AM/PM bit with logic one being PM. In the 24-hour mode, bit 5 is the second 10-hour bit (20–23 hours).
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