Dear all, sorry for so much question. I am using P89c51rd2 As i want to counter the operation time of the device. And the counter data is store in ram when the device power off, all Any method can i keep the counter data even power off?
You need some sort of writable non-volatile memory; eg, in no particular order, EEPROM (aka E2PROM) FRAM Battery-backed SRAM Flash (not generally a good choice for such applications) Magnetic Core Note that Maxim/Dallas have some devices specifically designed for this particular application. Or perhaps an electro-mechanical or electro-chemical devce...