DS1678S Maxim Integrated Products, DS1678S Datasheet - Page 10

• 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
once any events that are being recorded have completed. The value in the MIP and ME bits will remain a
1 until the mission has completed, even if they are written to a 0. Upon initiation of an event log mission
by either method, the DS1678 will set the Mission-in-Progress (MIP) bit in the Control register to a one.
It should be noted that the MEM CLR bit of the Status register must be a one in order to start an event
log mission. This means that the Event Log memory, the Event Count, Elapsed Time Counter, Address
Pointer, and Start Time Stamp registers are cleared of data (all zero’s) so that an end user can not turn the
logger on and off to avoid recording events. Once the mission is stopped, the memory must be cleared in
order to start a new mission.
The time at which the first event log sample is measured is dependent upon the way the mission is
started. The first way to start a mission is with a delayed start by writing a 1 to the ME bit. The ME bit
will only be able to be written to a 1 if the MEM CLR bit is set to a 1. The mission will have a delayed
start until the first event occurs by activating the
pin. If the mission starts because the ME bit is set
INT
to a one and the
pin is activated, the MIP bit in the status register is set to a one, the current
INT
time/date is written to the start time stamp register, the event 0 elapsed time from last event bytes in the
time/date stamp are both written with zeros, the event count register will be incremented and the elapsed
time counter will start incrementing based on the settings in the DISx bits of the control register.
Subsequent events will be 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
pin being
INT
activated.
The second way to start a mission is write a 1 to the MIP bit of the status register over the 2-wire
interface, which will automatically write a 1 to the ME bit of the control register. This start mission
command will be ignored and no action taken if the MEM CLR bit is not set to a 1. When the MIP bit is
written to a 1 and the ME bit is set to a 1, the mission is started by loading the current time/date into the
start time stamp, the event 0 elapsed time from last event bytes in the time/date stamp are both written
with zeros, the event count register will be incremented and the elapsed time counter will start
incrementing based on the settings in the DISx bits of the control register. The first event will then be
logged as the duration of time since the start time. All subsequent events will then be logged as the
duration of time since the previous event.
The user has two options for dealing with the potential occurrence of a data overrun (i.e., more than 1024
total event logs in the event log memory) (See Figure 8). The first option is to enable the rollover feature
of the DS1678. This is accomplished by setting the rollover bit (bit 3 of the control register) to 1. When
the rollover feature is enabled, new data is written over previous data, starting with the start time stamp
register as if a new mission is starting.
The one difference with a time/date stamp from a rollover compared to a new mission start is that the two
bytes after the time/date stamp, event 0 elapsed time from last event, will have the elapsed time since
event 1024 of the event log memory. This is to allow the user to recover the information recorded prior to
the rollover. At the start of a mission, the value in these two bytes will be all zeros since there was no
previous event to have an elapsed time from.
The next event will have its elapsed time since the new time/date stamp recorded in event log memory
locations 0000h and 0001h as before. For example, if the event log memory has been completely filled
(i.e., 1024 event logs have been recorded in the event log memory) the next event will cause a new
time/date stamp to be written to the start time stamp register and the elapsed time since event 1024
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