Rainbow Electronics DS1678 - Manual (Page 9)

DS1678
9 of 26
DS1678 EVENT ELAPSED TIME DURATION Figure 2b
ADDRESS REGISTER
0000 Event 1 Elapsed Time from Last Event Counter LSB
0001 Event 1 Elapsed Time from Last Event Counter MSB
0002 Event 2 Elapsed Time from Last Event Counter LSB
0003 Event 2 Elapsed Time from Last Event Counter MSB
0004
¯
07FB
¯
07FC Event 1023 Elapsed Time from Last Event Counter LSB
07FD Event 1023 Elapsed Time from Last Event Counter MSB
07FE Event 1024 Elapsed Time from Last Event Counter LSB
07FF Event 1024 Elapsed Time from Last Event Counter MSB
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 TR0 bit set to a 1 and TR1 bit set to a 0, the
INT signal will be activated on the falling
edge of the input signal. With the TR0 bit set to a 0 and the TR1 bit set to a 1, the INT pin will be
activated on the rising edge of the input signal. With both TR0 and TR1 bits set to 1, the INT pin will be
activated on both the falling and rising edges to allow for the measurement of on/off type events and their
duration’s. If TR0 and TR1 are both set to 0, nothing will happen when the
INT pin is toggled and a
mission will not start. This is an illegal state and the mission will not start without a valid value in the
TRx bits prior to attempting to start the mission.
During an event log mission, every time the INT pin 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 will automatically increment to 42h where the
event log memory address MSB data will be written. The data from the event log memory location
corresponding to the address written into main memory locations 41h and 42h will be available in
location 43h to be read. The event log data is located at addresses 0000h to 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 figure
2b 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 will allow 1024 events to be logged.
A event log mission can be initiated via two different methods (See Figure 7); by a host writing a 1 to the
MIP bit of the status register over the serial interface which automatically sets the mission enable bit in
the control register to a 1 or by activating the
INT input when the mission enable bit in the control
register is set to a one. The elapsed time between events recorded during an event log mission is equal to
the value written to the event logger memory multiplied by one second, minute, or hour depending on
which one of the three is selected in the DISx bits of the control register. Writing a 0 to the MIP bit in the
Status register completes the mission and automatically writes a 0 to the ME bit in the control register