i m working on a project with 89c51rd2.
my problem is how to store some datas in memory...
a passwoed for example, i store a defult value for the password when i programming. and i want the user can change the password. but if the user shuts down the device or wants to change batteries then the user works the device again, the password will take the default value again.
how can i solve this? im using C language with keil.
i cant store any values in code memory. can the data memory remember the value?
Where is the 8051's static memory?
i want to select an address an store the password there. and i wont use a default value. But the problem is which memory of 8051 should i use, and how can i use it.
i wanna select an address and when program starting up i will check that address, if there is no value, i will store 1234 value into there as password. when user wants to change the password i will change the value of that address.
well can i select an address in code segment(or any memory space which dont forget the value) and how can i store a value into there? eg. i wanna store a byte to FFF0 address in code segment. is it possible?
If you really just need to preserve data while changing the battery - ie, just for a brief time - have you considered just using a large capacitor for backup power?
Possibly also putting the processor (and other parts of the system) into a low-power mode during that time...?
Changing battery was just an example
I thought to use 1F capacitor. But if user remove the power for long time. eg: a week...
And! of course i saw the datasheet of AT89C51RD2 many times in last 3 days. I saw nothing about this thread
You may have seen it, but you don't seem to have actually taken any time to study it!
www.atmel.com/.../doc4235.pdf
Right there on the front page, it says:
"• On-chip 2048 Bytes EEPROM Block for Data Storage (AT89C51ED2 Only)"
So that directly answers you question as to whether such a thing is available!
It also says:
"• 2048 Bytes Boot ROM Contains Low Level Flash Programming Routines"
So you have the facility for your code to write to the Flash.
And, on the product page in Atmel's website:
"
Of course not! Datasheets tell you the capabilities of the chip; it's up to you to think about how those capabilities could be applied to solve your particular problem