DS1682 Datasheet, PDF (8/14 Pages) Dallas Semiconductor – Total Elapsed Time Recorder with Alarm

DS1682
Total-Elapsed-Time Recorder
with Alarm
Event Logging
When the DS1682 is powered up, the event time and
count values recorded in the EEPROM are transferred to
the ETC and event counter, and the device waits for an
event. When an event triggers the input by transitioning
the EVENT pin from a low to a high level, the following
occurs:
1) The RC oscillator starts.
2) The alarm, ETC, and event counter are transferred
from EEPROM to RAM.
3) Note: Reading the RAM during the transfer results in
invalid data.
4) After t_ES, the ETC increments. An event greater than
t_G but less than t_ES increments the event counter, but
not the ETC (zero-length event).
5) The ETC increments every t_EI. The ETC holds time in
quarter-second resolution.
6) When the EVENT pin goes low, the event counter
increments, the oscillator stops, and the ETC and
event counter are transferred to EEPROM. The 2-wire
bus is not available for t_EW.
The ETC stops counting and does not roll over once
FFFFFFFFh, or approximately 34 years, is reached. See
Figure 5 for timing.
Device Setup
Once installed in a system, the DS1682 can be pro-
grammed to record events as required by the application,
and can be tested by generating events and monitoring
the results. Afterwards, it can be “locked” to prevent
alteration of the event and alarm registers and the alarm
condition.
The following is a typical sequence:
1) Write the configuration register, alarm registers, and
user memory to the desired values.
2) Write-protect the alarm, ETC, and event counter regis-
ters with the write disable command if needed.
3) Write-protect the user memory with the write-memory-
disable command, if needed.
4) Issue a reset (described in the Reset Command section).
The alarm, ETC and event counter registers, and user
memory, once locked, cannot be changed.
Upon reset, the ETC and event counter registers are
cleared. The device clears the RE bit, and the configu-
ration register becomes read-only. Additional resets are
ignored.
tG
EVENT INPUT
tEI
INTERNAL EVENT
CLOCK
tES
Figure 5. Event Input Timing
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