Hi Guys, I don't know if this question is to be asked here or no but anyway- Is there anybody who have used NV RAM of DS12887RTC. It turned out that 3 of my RTCs were working for some time properly and then their RAM content disappeared- I am doing some new code to store data on NV RAM and checking it with incoming data(through serial) So needed to remove my micro controller for few times to reprogram it However after a while RTC content used to disappear And even if I run my "First_Run"(to load RTC) I can't get that data on RTC. If anybody is experienced with NV RAM?RTC please help me. Thank you in advance
Thanks Westermark I guess the diagram should have been in code form Anyway can you suggest any reset supervisor IC or Reset chip One more thing I checked the voltage levels(had DMM connected for all the time) at NVRAM they were always at around 4.5V to 5.10V however not at the time of switch off (removing plug)
It seems like you where trying to draw this:
Vcc | | | Capacitor(10uF,25V) | |----------------------(Reset pin of uC) | Resistor(8k1) | | GND
But a simple RC reset is not recommended for several reasons. The voltage over the capacitor is changing slowly, so the processor may be reset multiple times in case there is noise in the Vcc and the reset input doesn't have a wide enough hysterese.
Another problem is that the reset is assymetrical. You want the reset signal to be activated while waiting for the supply voltage to rise on startup. But also when the supply voltage is slowly dropping after you have disconnected the power - or the battery voltage has dropped below the safe working range.
It is recommended that you use a dedicated reset chip. That may have a open-collector or a totem output, but will give a distinct toggling beteen active and inactive, and they will react to any irregularities in the supply voltage.
Having the processor run at too low voltages, or to try to program EEPROM, flash or battery-backed memory below the minimum required write voltage for the memory, may result in destroyed memory contents and may potentially activate read-protect and/or write-protect features of the memory.
Sorry for that diagram but while typing it was looking good but after preview it is fuzzy Please try to understand it
Hello Erik Thanks for your interest Here is how my circuit is Vcc | | | Capacitor(10uF,25V) | |----------------------(Reset pin of uC) | Resistor(8k1) | | GND
Can you please tell me if there is any problem with this circuit and my NVRAM What can be the problem with this circuit in general it used to work fine
a RC does NOT reset on power down and the uC just run wild.
Erik
Sorry but can you elaborate more I haven't implemented any supervisor and even I don't have reset button - just an RC combination
do you have a real supervisor in your circuit or a stupid RC reset.
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