Since there are only 1024 locations in the memory, there are 1024 addresses, they're numbered 0 through 1023. And that number, that function returns the contents of that address, so all the addresses are numbered.
And you pass it an argument, which is an address, which is just a number. So the way you read an address is you call this function called EEPROM.read. And each address is one byte, so we call byte addressable, meaning every address has one byte in it. They provide library functions to access the EEPROM you access one address at a time. Even after you unplug your Arduino, plug it back in. So the code itself is sitting on the Flash, plus the boot-loader.īut the EEPROM is a place where you might store settings, or variables, or something like that, that you want to save time and time again. But EEPROM is better than flash.įlash on our ATMega is used for the program or sketch itself. Now this isn't as good as hard disk, disk has a lot more than that. So maybe a flash might be tens of thousands of write cycles, EEPROM would be a hundred thousand After that eventually that address won't work anymore.Īnd, the memory will just fail. So, what that means is if you've got Flash, and you've got a particular address in the Flash, you write to that address 10,000 times. Flash will last tens of thousands of write cycles.
It's byte writable so you can do one byte at a time.Īnd EEPROM supports many more write cycles than flash so even though both don't last forever. So this wastes time and things like this but that's the way it's organized. Which maybe you don't even need to write to the whole block. So if you want to write to one byte, you've gotta write to the whole block. Now with flash, you can't actually write a byte at a time. So in fact, EEPROM technology is similar to flash.īut it's more flexible as you can write a single byte at a time. When you turn on power again, it still has the same memory. The microcontroller on the Arduino and Genuino AVR based board has EEPROM: memory whose values are kept when the board is turned off (like a tiny hard drive).Ī disk is non-volatile memory, like flash which is also a non-volatile memory EEPROM - Electronically Erasable Programmable Read-Only Memory
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