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Using NVRAM in embedded projects

NVRAM(Non-Volatile Random Access Memory) is one of non-volatile memory selections. This may be alternative to EEPROM back up memory. NVRAM chips can be used for nonvolatile memory storage with many benefits comparing to EEPROM. Main benefit is that NVRAM chips work like static RAM. Actually they are RAM just they contain lithium cell battery for retaining RAM contents when main power is switched off. The backup memory can store contents as long as battery provides power. NVRAM chips doesn’t require much power, backup can be guaranteed for up to ten years.

For instance lets take Dallas NVRAM chip DS1225.



It contains 64k(8k x 8) of RAM memory. Chip has internal battery built in so you don’t have to take care about additional backup power. Memory can hold contents about 10 years without relying only on internal battery. Using NVRAM gives unlimited write cycles, while EEPROM is limited to like 100000 times. Also content is protected during sudden external power loss. Main benefits I can see is operation speed and unlimited write cycles. IF application needs constantly update contents of backup memory, EEPROM 100000 write cycle limit may exceed very fast. In this case it is better to use NVRAM. Same situation with speed. EEPROM is quite slow memory and sometimes there would not be enough performance to store incoming backup data. NVRAM speed is same as SRAM, so there can be stored not only back up data, but application itself.

DS1225 NVRAM also match pin-out with 2764 and 2864 EEPROM. Chip. So it is easy to substitute chips if needed.

Truly speaking NVRAM memory isn’t that popular as there are more nonvolatile alternatives like FLASH memory which is providing really high performance for low price. But NVRAM with static RAM inside stil provides significant speed comparing to FLASH.

Last word about confusing. Like many manufacturers like to write Dallas Semiconductors like to describe memory size in bits like on DS1225 they write 64K, but actually it is 8 – kilobyte memory chip. Dont get tricked.

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