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AN1176.0
June 20, 2005
corrections, see the troubleshooting section at the end of
this document.
If the COM port number is known in advance (it may be
located by looking in the Hardware Device Manager on your
PC while the board is plugged in), it may be selected
manually by using the setup menu. The software may then
be used normally.
Software Time/Date Operation
After opening the RTC program, you will be viewing the RTC
Data Analysis Screen. The RTC device requires an initial
write to the clock/calendar registers to begin keeping time.
Open the “Set RTC date and time” window and by clicking
on the clock icon in the menu bar. The easiest way to set the
current time is to click the “Set date and time from PC clock”
button, although the time and date can be manually entered
using the calendar and time windows. Also choose the time
format, either 12- or 24-hour. When complete, click on
“Done”, bringing you back to the RTC data analyzer window.
Next, click on the “Poll RTC” button. The PC Time, RTC
Time, and RTC Deviation windows should constantly update
with their respective information. This is the normal mode for
RTC operation/monitoring. If the RTC Time fails to update or
is not set correctly, use the following troubleshooting steps.
1.
RTC time stuck at 12:00:00 and not advancing
The
proper time was not initially written to the RTC registers.
Go back to the “Set RTC Time and Date” window and set
the time again. Also, be sure to check the USB cable
hookup and daughtercard connections to insure these
are correct.
2.
RTC time is showing widely varying readings, not
consistent and advancing
Most likely the eval board
was plugged in after the software was started, which
causes issues. Exit the software program (File > Exit, or
the X in the upper right corner), and re-open the program.
It should detect the board and function correctly.
As the program polls the RTC and updates time, there will be
a difference between the RTC time and the PC time due to
finite PC communications delays. This should be a constant
+1 or -1 second difference, and the window will alternately
display between zero and one-second error.
As the RTC or the PC clock drifts, the RTC time window will
change color. If the RTC time is faster than PC time, the
window will turn red, first light red then dark red, as the error
increases. If the RTC time is slower than PC time, the
window will turn blue, first light blue then dark blue, as the
error increases.
During Polling the temperature of the daughtercard is
displayed and updated once per second as well. The ATR
register is also displayed, but will likely not change unless
Temperature Compensation feature has been enabled
(discussed later).
The Polling can be turned off by clicking on the polling button
again. The RTC device will still be keeping time, and when
Polling is turned on again, it will display the RTC current
time.
Modifying RTC Registers
Open the RTC Register screen using the shortcut key in the
menu bar (the group of 1s and 0s). The RTC Registers are
available using the pulldown menu on the left. Using these
registers, the functions of the RTC device can be enabled,
modified, or monitored, including:
• Frequency output
• Alarm settings
• Analog Trimming Registers (ATR)
• Digital Trimming Registers (DTR)
• Event-Detection (ISL1209 only)
The clock/calendar registers are available also, but are more
easily modified by using the clock/calendar window.
Once the correct register is located, the byte is displayed in
the horizontal window along with its hex value. Changes to
the individual bits can be made by clicking on a location. A
zero is indicated with a white background, and a one is
indicated by yellow background. Once the value of the byte
is set, the byte is written to non-volatile memory by clicking
on “Write”. A register value can be read by clicking on
“Read”.
Using the RTC Deviation/Temperature Recorder
The program is able to record continuous time
measurements of the RTC deviation from PC Clock and the
board temperature and create a plot of the results. Time
frames from a few minutes to many days are possible. From
the RTC Data Analysis screen, first select the deviation
range from the lower right set of pulldown windows. The
Temperature Range and Time Base should also be set as
desired from their pulldown windows.
Set the RTC time from the PC time as described above (see
Software Time/Date Operation section). This will insure the
PC time is close to the RTC time to begin recording.
To begin recording, select “Start” from the “Record Data”
pulldown menu (or click on the right arrow in the menu bar).
Data will be recorded periodically until the end of the time
frame selected or until the Stop function is selected. Note
that multiple samples are recorded and averaged before
being plotted on the chart recorder.
The status of the recorder is shown in the windows at the
bottom of the RTC Data Analysis screen. These windows will
continually update with information on the data recording.
Recorded data can be saved to a file, as well as imported
from a saved data file.
Application Note 1176
