Rockwell Automation 1762-Lxxxx MicroLogix 1200 Programmable Controllers - Manual (Page 90)

Publication 1762-UM001G-EN-P - March 2011
6-2 Use Real-time Clock and Memory Modules
The following table indicates the accuracy of the RTC for various
temperatures.
Write Data to the Real-time Clock
When valid data is sent to the real-time clock from the programming device or
another controller, the new values take effect immediately.
The real-time clock does not recognize or accept invalid date or time data.
Use the Disable Clock button in your RSLogix programming software to
disable the real-time clock before storing a module. This decreases the drain
on the RTC battery during storage.
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 is lost.
Table 6.1 RTC Accuracy
Ambient Temperature
Accuracy
(1)
(1) These numbers are maximum worst case values over a 31-day month.
0 °C (+32 °F) +34 … -70 seconds/month
+25 °C (+77 °F) +36 … -68 seconds/month
+40 °C (+104 °F) +29 … -75 seconds/month
+55 °C (+131 °F) -133 … -237 seconds/month
Life Span Operating Temperature
Storage Temperature
(1)
(1) Stored for six months.
5 years 0…40 °C (32 … 104 °F) -40 … 60 °C (-40 … 140 °F)