Rockwell Automation Publication 1766-UM001O-EN-P - September 2021 123
Chapter 6
Real-Time Clock and Memory Modules
The MicroLogix 1400 controller has a built-in real-time clock (RTC). You can
order a memory module as an accessory.
One type of memory module is available for use with the MicroLogix 1400
controller.
Real-Time Clock Operation Operation at Power-up and Entering a Run or Test Mode
At power-up and when the controller enters a run or test mode, the values
(date, time and status) of the RTC are written to the RTC Function File in the
controller.
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 allow you to load or store invalid date or time data.
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
Topic Page
Real-Time Clock Operation 123
Memory Module Operation 124
For more information on Real-Time Clock Function File and Memory Module
Information File, see MicroLogix 1400 Programmable Controllers Instruction Set
Reference Manual, publication 1766-RM001
.
Catalog Number Function Memory Size
1766-MM1 Memory Module 384 KB
RTC Accuracy
Ambient Temperature
Accuracy
(1)
(1) These numbers are maximum worst case values over a 31-day month.
0 °C (32 °F) -13…-121 seconds/month
25 °C (77 °F) +54…-5 seconds/month
40 °C (104 °F) +29…-78 seconds/month
55 °C (131 °F) -43…-150 seconds/month
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