sharing 3-wire eeprom

[tishri]

hi guys,

i would like to ask if it is possible that

PIC16f877 only reads the 93c66 3-wire eeprom.
and the other pic16f84a writes/manages data to 3-wire eeprom.
they both share only one external eeprom.

Thank you

[Jerson]

It is possible, but you will need some form of arbitration between the 2 PICs. This makes sure that only one PIC accesses the EEPROM at any point in time. You could think of a single port pin that is used to achieve this. The port is always in INPUT mode. Before it takes control of the EEPROM, it checks to see if the port pin is HIGH. It then puts the port to OUTPUT mode and signals a LOW to the otherside. Now it can access the EEPROM. A similar thing can happen on the other PIC when it needs access to the EEPROM. This is just an overview, of course there are finer details you have to look into when you implement it.