adccommunitymod (AutomationDirect) asked a question.
BRX SD Card
Created Date: September 13,2018
Created By: pbw
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I have a bunch of string that are in retentive memory and its very important that the PLC never losses them. I have code that saves them to the SD Card on a Save Event and reads them on a Read Event. I'd like to automatically refresh them ONLY if the retentive memory was lost. Is there a system bit that will signify if the retentive memory has been lost?
Created Date: September 13,2018
Created by: pbw
I have a bunch of string that are in retentive memory and its very important that the PLC never losses them. I have code that saves them to the SD Card on a Save Event and reads them on a Read Event.
I'd like to automatically refresh them ONLY if the retentive memory was lost. Is there a system bit that will signify if the retentive memory has been lost?
Created Date: September 13,2018
Created by: franji1
ST149 $BatteryLow. When you power-up and that bit is ON, your retentive data is questionable.
There is a super-capacitor that keeps the RAM state retained when the battery is low, but that is only for the purpose of replacing the battery (i.e. you have the battery in your hand, you power down the PLC, you replace the battery, you power back up). Super-capacitor retentive time is spec 'ed in HOURs of time. Battery backup is spec 'ed in YEARs.
Created Date: September 13,2018
Created by: BobO
There really isn't anything directly available to the program. It gets logged. You could check ST1022. We set that when the clock has been set, and like everything, it gets cleared when there was a retentive memory failure.
Created Date: September 13,2018
Created by: pbw
I think I'll issue a warning when the battery gets low and a option to restore the memory from the card when ST1022 gets cleared.
I appreciate your help, thanks.