The CPC Ethernet card has been designed using the Crystal CS8900a integrated ethernet chip. The Interface onto this chip is via an 8255 PPI to get the required address lines which are not available with the I/O address lines of the CPC (there is simply not enough of them). The has led to a simple interface design along the same lines as that used for the IDE/8255 interface.
Upon seeing other 8-bit systems have an ethernet card I sought out the requirements which could implement an integrated solution and found that the CS8900a was one such solution. There is another one using the RealTek chip (but access to them was unavailable at the time).
The Software to drive the ethernet card is not as difficult as one might think. These routines only setup the MAC address of the CS8900a and communicate this with the outside world and the perform simple packet delivery and reception handling.
The development of the card has reached a point where on the wiki forum there is a topic showing a completed prototype. Testing of this prototype has not gone as expected when it became evident that one of the CS8900a control lines was not connected, so it would not work consistently as expected.
I have now built and tested a prototype with simple communication of data in/out of the device.