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fingerprint doorlock project

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esraa mango

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hi all
i need help , i want to Connect PIC18f452 with external RAM using ISIS Proteus
and write program using the microbasic such that read and write from and to RAM

how i can connect them
and what is the program i need to read and write
thanks a lot :)
 

why do you wanted to add external RAM to PIC18F452 .?
 

i need it ,
i need to use the external RAM
to compare the fingerprint store in it when someone put his finger on the machine ,with the original one which store in ROM

 

Hi,

Some of PIC18 series have External Memory Interface (EMI) but PIC18F452 hasn't. https://ww1.microchip.com/downloads/en/AppNotes/00869b.pdf

If you still think to use PIC18F452, you must write your code to manually control data bus and control bus for RAM because it hasn't EMI module.

By the way, which fingerprint sensor are you going to use?
 

aha ok , i see

we want to use SM630 scanner

Added after 5 minutes:

there is another thing ,,,
i connected the PIC with external ROM directly without need for logic interface
using the simulation , and it work correct without any problem
i read from it.

by the way i used PIC18f452
why i need the logic interface with RAM ??
 

You know that although EMI is an integrated module to connect external memory, it needs logic interface (latch) when EMI is wanted to use. However, PIC18F452 hasn't EMI and you can use PIC18F452 with or without any logic interfaces. If you use latch circuits, you save up pins of the microcontroller but external memory read speed and write speed of the microcontroller decrease and you have more complex circuit and pcb.
 
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