Allen-Bradley MicroLogix 1200 Reference Manual page 48

3-4 Function Files
Publication 1762-RM001C-EN-P
Writing 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. In
RSLogix 500, click on Set Date & Time in the RTC Function File screen to
set the RTC time to the current time on your PC.
You can use a MSG instruction to write RTC data from one
NOTE
controller to another to synchronize time. To send (write)
RTC data, use RTC:0 as the source. This feature not
available with the Series A controllers.
The real-time clock does not allow you to load or store invalid date or
time data.
Use the Disable Clock button in your programming device
NOTE
to disable the real-time clock before storing a module.
This decreases the drain on the 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
represents the status of the RTC battery. When the battery is low, the
indicator bit is set (1). This means that the battery will fail in less than 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.
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.
Table 3.4 RTC Battery Life Expectancy
Battery State Temperature
Operating 0°C to +40°C (+32°F to +104°F)
Storage -40°C to +25°C (-40°F to +77°F)
+26°C to +60°C (+79°F to +140°F)
(1) The operating life of the battery is based on 6 months of storage time before the real-time clock is used.
Time Duration
(1)
5 years
5 years minimum
3 years minimum