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EEPROM of a PIC16F877A...

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josh1245

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hello!

can i please know how does the EEPROM of PIC16F877A read and write? I am doing a project which involves saving passwords, so how many four character passwords can it save?
Does a 4*4 keypad work with interrupts?
 

PIC16F877A has 256 bytes of EEPROM storage. If each character takes 1 byte, each password takes 4 bytes. So, you can save 64 passwords. You can save more if, instead of assigning 1 byte for each character, you assign 4 bits.
Does a 4*4 keypad work with interrupts?
Click to expand...
Do you mean you want an interrupt to be generated upon a key press?

Hope this helps.
Tahmid.
 

thanks for your reply and yes, I wanted an interrupt to be generated upon a key press once the system is on sleep mode, furthermore we are targeting to save many no of passwords, (for eg. 1234) i.e. 4 digit characters passwords.. more like passcodes... so what is the best way to do this? and can u assign 4 bits for characters? this is my very first project,, besides um new to working with PICs.. so your help is appreciated :)
 

How many passcodes do you need to save? If the required number is less than 64 (or equal to 64), you can assign 1 byte to each character simply and save the passcodes on the PIC EEPROM.
 

PORTB higher nibble change on interrupt can use for 4X4 keypad interface.
internal eeprom read and write is also possible with library functions or user functions.
 

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