The Allen-Bradley 1764-MM1RTC is a component of the 1764 MicroLogix product family. This module is specifically a combination module that has a Real-time clock and 8KB memory module. This module is attached to the terminal base, which is automatically detected by the controller.

The Real Time Clock is typically used to provide an accurate time base, to implement applications that references the controller’s date and time. Some applications that depend on this feature include device scheduling in Heating, Ventilation and Air Conditioning (HVAC) applications, Water process to control duplex and triplex pump sets, automatic triggering of logic and sequences. This module provides the year, month, day of month, day of week, hour, minute.

The memory module complements the integrated memory of the processor. More importantly, the memory module enables data protection and allows saving of the user program independent of the battery charge. With this, unwanted deletion of program may be avoided when the Lithium battery loses charge. Additionally, the memory module may be transferred to another control to run the program. With the use of this module, the controller loads the program from the memory module rather than the RAM memory area that is retained by the Lithium battery.

The accuracy of the Real-Time clock depends on the quartz crystal’s stability. The mentioned accuracy depends on the operating temperature to where the MicroLogix system is installed. For Temperature range 0°C (+32°F), the accuracy is +34 to -70 seconds/month. For +25°C (+77°F), +36 to -68 seconds/month. For +40°C (+104°F), +29 to -75 seconds/month and +55°C (+131°F), -133 to -237 seconds/month.

The 1764-MM1RTC is a memory module and a real-time clock that belongs to the 1764 series and it is manufactured and designed by Allen-Bradley. It is a MicroLogix Controller option component that features an integrated real-time clock and memory module with size of 8 Kilobytes. The importance of the Allen-Bradley 1764-MM1RTC and real-time clock memory module lies in the fact that it provides a time-base for all the controller functions that require a real-time coordination of events. This module provides the year, month, day of month, day of week, hour, minute, and additional information to the controller. The memory area of this module stores programs and data, transports programs to be used with other controllers, provides security for critical applications, compares programs, and offers data file and memory module protection.

The accuracy of the real-time clock function can vary significantly depending on its temperature. For a temperature range of 0 to 40 degrees Celsius, the accuracy can vary from 34 to 70 seconds per month and 29 to 75 seconds per month. The battery of the Allen-Bradley 1764-MM1RTC and real-time clock memory module is not replaceable, but this module has a battery indicator, and when it shows that the battery signal is low, it means that the battery will fail within 14 days. The battery life expectancy when operating at a temperature of 0 to 40 degrees Celsius is about 5 years. Both the memory module and real-time clock can be removed without causing damage to the host controller. Once the memory module has been removed and reinserted, the module will not recognize it until a power cycle occurs.