One of the things provided for within Amélie is the possibility of expansion. For example, there is no analogue-to-digital convertor. This could be added, and mapped in at an unused address. Alternatively, it might be decided to add a second 6522 to provide more digital I/O. In fact, by adding a second 6522 to the unused address, and replacing the latch with another 6522 (four lines of that could drive the LEDs), we'd have 48 digital I/O lines (minus two for the I²C and four for the indicators , thus leaving 42).

This is part of the "open spec" I was talking about. You don't get a CPU and fixed I/O, you can customise to your specific needs. Because the data bus, control signals, and part of the address bus are made accessible, expansion can be added "later". All that is required is a new EPROM containing an updated BIOS and application code.

The memory decoding will provide preselected decoding for several additional devices; and these decoded "chip select" signals will be available on the expansion connector.

The diagram above is the 26 pin DIL socket that provides the expansion signals. This has not yet been fixed - if the "options selector" is built onto the main board then USUSEL will be removed. It is likely that things will be jiggled around slightly and A6 added. The following description is based upon these changes...

The expansion connector is intended for adding additional core hardware to Amélie. Four expansion chip select lines are provided, and A0 to A6 provide addressing of 128 bytes within each 'slot'. If required, additional logic could split this further, i.e. using A6 to select a sub-device (such as two VIAs?).
The system clock is provided, as is the obligatory read/not-write. There is an IRQ input. Power (+5V DC) is also provided.