Micrologix 1400 RTC

Old No. 7

Member
Join Date
Jun 2010
Location
Ohio
Posts
173
I have an application where I'm trying to sync a HMI clock with the Micrologix RTC. I finally got everything working, but I found one fairly major issue. If you send the time/date while the RTC is disabled, the PLC will fault. What I would like to do is have the PLC program enable the RTC, but I don't think this is possible. The only way I can see is to enable it through RS Logix.
 
Apparently you can disable the RTC by writing all 0's to RTC Words 0 thru 5, which contain the date and time fields. I don't know, if you then write the current date and time into these fields, whether the clock will restart.
 
I did confirm that sending zeros to all the time/date fields will disable the RTC. Unfortunately, sending it time/date values when it is disabled will fault the PLC.

It's easy enough to prevent the fault by not sending values if the RTC:0/DS (disabled) bit is set but it sucks that there is no way to turn it back on through the program. Since it defaults off when you get a new PLC, I'm worried about our guys forgetting to turn on the RTC manually through RS Logix during startup.
 
The manual says the RTC:0/DS is read only. You can probably use that bit in logic to
only allow your HMI to write to the RTC when it's enabled.
 

Similar Topics

Hi There, We seem to be having issues with one of our MicroLogix 1400. It appears that after certain days, the RTC time automatically resets to...
Replies
6
Views
2,261
Hi everyone, I’ve been reading these boards for some time and have had many questions answered indirectly by the helpful members of this forum. I...
Replies
7
Views
3,941
I am using Micrologix 1400 with RSLogix 500 for the first time and having some trouble using the Real Time Clock - RTC. Reading the values is no...
Replies
2
Views
4,155
Hi, Could someone please check the file attached and advice if there is any thing else to be considered? Please note I have attached only part of...
Replies
2
Views
6,698
Hi, I am working with a Micrologix 1400 model 1766-L32BXB. With no input wires connected to the “in12” thru “in19”, I am getting 24 volts while...
Replies
4
Views
172
Back
Top Bottom