Avr Block Diagram - FIGnition FUZE Hardware Reference Manual

25. PC2. This is used as a column select 2 input. It can't be re-used unless the keyboard
scanning is disabled.
26. PC3. This is used as a column select 3 input. It can't be re-used unless the keyboard
scanning is disabled.
27. PC4. This is used as the LED output. It can be fully re-used if the track between the
pins of LK1 is cut. PC4 is part of the AVR's built-in I2C interface.
28. PC5. This pin is free.
Of all the pins on FIGnition's AVR chip, only Port D0, Port D3; Port D5 and Port C5 are
generally available for I/O. Port C4 can be used if the LK1 track is cut. Port D6 may have
some limited usage and some other I/O ports can be used with a corresponding loss of
basic FIGnition functionality.

8.2.2 AVR Block Diagram

The primary functional parts of FIGnition's AVR are shown in Fig 8.2.
FIGnition uses most of the AVR's hardware functionality:
• None of the Flash memory can be modified from User code, only via a firmware upgrade.
• The EEProm is fully available for user applications. It is possible to store a 1 block pro-
gram in the EEPRom; load and run it (though it won't run automatically).
• FIGnition's firmware at or below version 0.9.8 doesn't support user interrupts.
Fig 8.2