Internet PLC Forum

Archives => Archived Tech Support => Topic started by: support on October 27, 2005, 05:35:21 AM

Title: Using MX-RTC / MX-RTC Battery Life
Post by: support on October 27, 2005, 05:35:21 AM
MX-RTC is an optional battery backed real time clock module that you add between the 28pin SRAM and the 28pin socket on any T100MD+ or T100MX+ PLC. It keeps the real time clock running even when all power to the PLC has been shut down.

If you turn on DIP Switch #1 to the PLC, then MX-RTC will preserve the values of all the internal variables when power is removed. These includes A to Z, A$ o Z$, DM[1] to DM[4000], as well as timers  and counters present value.

There are also data and logic states that are NOT PRESERVED,such as the values of INPUT[], OUTPUT[], PWM output, DAC outputs and Stepper motor ouputs.  The PLC will reset all the outputs regardless of the presencee of MX-RTC. This is to prevent a situation where after a power failure, some outputs that should NOT be turned ON unless with some user intervention to ensure that it is safe to do so, became active due to its ON state before power failure.

As such a scenario may be hazardous, it was decided that the output logic states will not be preserved after a power on reset. However, all internal relay logic status are preserved. So if your program requires that an output must return to its pre-power down states, then you can turn on an internal relay first and the contact of the internal relay is then used to drive the output. This give a degree of control to the user to determine which output is allowed to be turned ON based on its pre-power down logic state. Similarly, all PWM output and DAC outputs will not be set to their pre-power down values, so the programmer must take this fact into consideration.
Title: MX-RTC Battery Life
Post by: support on June 18, 2007, 04:54:16 PM
Q: How Long does the battery last in MX-RTC?

a) MX-RTC contains Lithium battery that has shelf life of 10 years

b) When PLC is powered up, MX-RTC battery is not used. Hence if system is up most of the time then the battery life is determined by its shelf life.

c)  When power is not applied to the PLC with MX-RTC installed, the internal battery is used to keep the RTC running and maintain the contents of the RAM data. For system that are running in the day but turned OFF at night the battery life should last for 5 years or longer.

d) Battery inside MX-RTC is NOT rechargeable and NOT replaceable. The whole MX-RTC need to be replaced when its battery is depleted.

Title: Real Time Clock Application Demo Program
Post by: support on July 20, 2009, 12:50:13 PM
A demo .PC6 program based on some code fragment contributed by a user is posted at the following web page.

You can simply include the program into your own codes and then all you need to do is to use the relay contacts #17 to #24 as flags to either turn ON/OFF outputs or trigger custom functions to perform required tasks.
Title: Re:Using MX-RTC
Post by: garysdickinson on July 30, 2009, 12:09:54 AM
I have modified the demo program for improved reliability. I have added a routine to access the TIME[] registers to ensure that the correct time is returned.  I would be happy to e-mail my modified program.  Please let me know.

Gary Dickinson
Title: Re:Using MX-RTC
Post by: support on July 30, 2009, 08:58:04 AM
We will be happy to receive your contribution. Thank you very much! Please email to and we will post your modified version.

Update: We have just posted the latest contribution by Gary. Please download from the following link: