ISA Bus Interface

[nanoha]

Hello,
For my VHDL project, I need to study about the programming of ISA Bus Interface. Seems like the coding is divided into few sections.

Can anyone explain to me what is the function of those sections in ISA Bus:

• 8-bit adder
• Comparator
• Data register
• Data Path of ISA bus interface
• FSM controller for ISA bus interfacing

Thanks.

ps: I also appreciate if you can provided related link to me (I already Google but seems that I can't find the answer)