The current plan is to use a 3Com 3c509B ISA Ethernet card with the hardware that I plan to build and finally give the Color Computer Ethernet capabilities. One advantage of the 509B card is that is has off-loading capabilities in hardware for checksums. The 6809 in the CoCo can use all the help it can get! The other thing about this card is you can purchase them cheap from eBay. At least a year ago you still could... One site that I have found has some example drivers click here . For a detailed copy of the 3Com 3c509B hardware (zipped PDF) click here. Finally, this site has an IP Stack for use with microcontrollers.
Installed and configured latest version of WinCupl from Atmel web site (version 5.30.4). For this project I am going to use the same CPLD part (Atmel ATF1508AS 84 pin PLCC 20ns part). According to the WinCupl fitter tool there are 50 percent of the I/O pins still available and only 20 percent of the internal logic is being used. This should allow for the ISA bus logic to be included in the same part. Here is my latest CPLD code for this project. The link is here. This code does not yet have any ISA bus logic added at this point :)