DS1683_12 Datasheet, PDF (8/21 Pages) Maxim Integrated Products – Total-Elapsed-Time and Event Recorder with Alarm

DS1683
Total-Elapsed-Time and Event Recorder with Alarm
Event Logging
When the DS1683 is powered up, the internal oscilla-
tor starts; the ETC and Event Counter values, which are
recorded in the shadowed EEPROM bank memory, are
transferred to the ETC and Event Counter SRAM loca-
tions; and the device waits for an event (rising edge of
the EVENT signal). When an event triggers the input by
transitioning the EVENT pin from a low to a high level, the
following occur:
1) The ETC and Event Counter values are once again
transferred from shadowed EEPROM bank memory to
their SRAM counter locations.
2) After the glitch filtering and t_EI, the ETC SRAM counter
value increments. See Figure 2 for timing. An event
greater than time event minimum (t_G) but less than t_EI
(i.e., a low-high-low transition on EVENT < t_EI) incre-
ments the Event Counter SRAM value but not the ETC
SRAM value.
3) The ETC SRAM value increments every t_EI. The ETC
SRAM counter holds time in quarter-second resolution.
4) When the EVENT pin goes low, the Event Counter
SRAM value increments by one, the ETC SRAM coun-
ter stops incrementing, and the values from the ETC
and Event Counter SRAM locations are transferred to
their Shadowed EEPROM counterparts. The I²C bus
is not available for t_W.
The ETC value does not roll over when FFFFFFFFh, or
approximately 34 years, is reached. The Event Counter
value does not roll over when reaching a value of FFFFh.
While the EVENT pin is high, I²C write commands are
ignored, though I²C read commands are still possible.
Password Protection
From the factory, the DS1683 powers up without pass-
word protection enabled. The intent is to provide a
manufacturer an optional security feature to protect the
Configuration register, Alarm registers, User EEPROM,
ETC and Event Counter settings, and the Password Value
(PWV). The customer is not able to alter the Configuration
register, Alarm registers, ETC or Event Counter, User
EEPROM or Password Value settings if the password
conditions are not met.
The DS1683 password is stored in the 4-byte read-
only Password Value register, located at 1Ah–1Dh. The
default value for this register is FFFFFFFFh. To change
this value, a 4-byte I²C write command must be issued.
The 4 bytes of the new password must be issued with
the same I²C write command. Once the STOP of the I²C
write command is issued, the Password Value register is
updated with the new 4-byte value.
The Password Entry bytes (PWE) are where the user
enters the 4-byte password to unlock access to the
DS1683’s EEPROM locations. When writing the PWE
value, the user must issue a 4-byte I²C write command
starting at location 02h. This 4-byte value must match the
4-byte Password Value stored in registers 1Ah–1Dh.
tG
EVENT INPUT
tEI
INTERNAL EVENT
CLOCK
Figure 2. Event Input Timing
Maxim Integrated
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