Publication 1766-RM001A-EN-P - October 2008
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Function Files
The real-time clock does not allow you to load or store invalid date or
time data.
Real-Time Clock Accuracy
The following table indicates the expected accuracy of the real-time clock
for various temperatures.
RTC Battery Operation
The real-time clock uses the same replaceable battery that the controller
uses. The RTC Function File features a battery low indicator bit (RTC:0/
BL), which shows the status of the replacement battery. When the battery
is low, the indicator bit is set (1). This means that the battery wire
connector could be disconnected or if the battery is connected, the battery
may be ready to fail in the next two weeks. In the latter case, the
replacement battery needs to be replaced with a new one. When the
battery low indicator bit is clear (0), the battery level is acceptable.
TIP
Use the
Disable Clock
button in your programming device to disable the
real-time clock before storing a module. This decreases the drain on the
battery during storage.
Real-Time Clock Accuracy at Various Temperatures
Ambient Temperature
Accuracy
(1)
(1) These numbers are worst case values over a 31 day month.
0°C (+32°F)
-13…-121 seconds/month
+25°C (+77°F)
+54…-54 seconds/month
+40°C (+104°F)
+29…-78 seconds/month
+55°C (+131°F)
-43…-150 seconds/month
ATTENTION
Operating with a low battery indication for more than 14 days may result in
invalid RTC data if power is removed from the controller.
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