DS1678S+T&R Maxim Integrated Products, DS1678S+T&R Datasheet - Page 12

• Manufacturer Part Number: DS1678S+T&R
• Description: IC REAL TIME EVENT REC 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Time Event Recorderr

Specifications of DS1678S+T&R

• 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: Lead free / RoHS Compliant

DS1678 Real-Time Event Recorder
EVENT LOGGING
When the DS1678 event-logging function is enabled, the device is said to be on an “event-log mission”
until the event logging is stopped.
An event can be triggered one of three ways depending on the settings of the TRx bits in the Control
Register. With the TR0 bit set to one and the TR1 bit set to zero, INT is activated on the falling edge of
the input signal. With the TR0 bit set to zero and the TR1 bit set to one, INT is activated on the rising
edge of the input signal. With both TR0 and TR1 bits set to one, INT is activated on both the falling and
rising edges to allow for the measurement and duration of on/off type events. If TR0 and TR1 are both set
to zero, nothing happens when INT is toggled, and a mission does not start. This is an illegal state and the
mission does not start without a valid value in the TRx bits prior to attempting to start the mission.
During an event-log mission, every time INT is activated, the elapsed time from the last event is written
to the event-log memory pages. These memory pages are accessible through the data port in the main
memory. To access data via the data port, the LSB of the address location in the event-log memory is
written into 41h, the main memory address pointer automatically increments to 42h where the event-log
memory address MSB data is written. The data from the event-log memory location corresponding to the
address written into main memory locations 41h and 42h is available in location 43h to be read. The
event-log data is located at addresses 0000h–07FFh in the event-log memory. The LSB of the first event
duration is written to address location 0000h. The MSB of the first event duration is written to address
location 0001h. The LSB of the second event is written to address location 0002h. The MSB of the
second event duration is written to address location 0003h (see Table 3 for more details). Likewise, the
address is incremented with each additional event duration. A total of 2048 registers have been reserved
for event-log data, which allow 1024 events to be logged.
An event-log mission can be initiated by two methods (Figure 3). The first method to start a mission is
with a delayed start. This is accomplished by writing a one to the ME bit. The mission starts when the
first event occurs by activating INT. When INT is activated, the MIP bit in the Status Register is set to
one, the current time/date is written to the Start Time Stamp Register, and the Event 0 Rollover Stamp is
written to zero. The Event Counter Register is incremented and the ETC starts. Subsequent events are
logged as the duration of time from the previous event by writing the contents of the ETC into the event-
log memory when that subsequent event is triggered by the activated INT pin. Note: The ME bit can only
be written to one and a mission started if the MEM CLR bit is set to one.
2
The second way to start a mission is write a one to the MIP bit of the Status Register over the I
C
interface. When MIP is written to one, the ME bit in the Control Register is automatically set to one.
When the MIP bit is written to one, the mission is started by loading the current time/date into the start
time stamp, and the Event 0 Rollover Stamp is written to zero. The Event Counter Register is
incremented and the ETC starts incrementing. The first event is then logged as the duration of time since
the start time. All subsequent events are then logged as the duration of time since the previous event.
Note: The MIP bit can only be written to one and a mission started if the MEM CLR bit is set to one.
The MEM CLR bit of the Status Register must be a one to start an event-log mission. This means that the
Event-Log Memory, Event Count, ETC, Address Pointer, and Start Time Stamp registers are cleared of
data (all zeros) so that an end user cannot turn the logger on and off to avoid recording events. Once the
mission is stopped, the memory must be cleared to start a new mission.
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