> I have done a program for the PIC 16C84, It's very simple and not use the
> EEPROM location (only the TMR0). Can I compile this program on a PIC16C620,
> if the memory is enough , without modify?

Not quite:

[1] You will need to change the code to use a register-start address of $20
    rather than $0C.

[2] If you use PORTA, you'll have to set CMCON to enable it.

Other than those details you should be okay.