Rockwell Automation 1764-xxxx MICROLOGIX 1500 PROGRAMMABLE CONTROLLERS - Manual (Page 104)

Publication 1764-UM001B-EN-P - April 2002
6-2 Using Real-Time Clock and Memory Modules
Accuracy
The following table indicates the expected accuracy of the real-time
clock at various temperatures.
Writing Data to the Real-Time Clock
When valid data is sent to the real-time clock from the programming
device, the new values take effect immediately.
The real-time clock does not allow you to write invalid date or time
data.
RTC Battery Operation
The real-time clock has an internal battery that is not replaceable. The
RTC Function File features a battery low indicator bit (RTC:0/BL),
which shows the status of the RTC battery. When the battery is low,
the indicator bit is set (1). This means that the battery may fail within
14 days and the real-time clock module needs to be replaced. When
the battery low indicator bit is clear (0), the battery level is acceptable
or a real-time clock is not attached.
If the RTC battery is low and the controller is powered, the RTC
operates normally. If the controller power is removed and the RTC
battery is low, RTC data may be lost.
Ambient Temperature
Accuracy
(1)
(1) These numbers are expected worst case values over a 31 day month.
0°C (+32°F) +34 to -70 seconds/month
+25°C (+77°F) +36 to -68 seconds/month
+40°C (+104°F) +29 to -75 seconds/month
+55°C (+131°F) -133 to -237 seconds/month