DS1682 datasheet(8/14 Pages) MAXIM

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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 tES, the ETC increments. An event greater than

tG but less than tES increments the event counter, but

not the ETC (zero-length event).

5) The ETC increments every tEI. 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 tEW.

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.

Figure 5. Event Input Timing

INTERNAL EVENT

CLOCK

tES

tEI

EVENT INPUT

DS1682

Total-Elapsed-Time Recorder

with Alarm

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