I’ve always found it very difficult to get a quick overview of the KNX telegram structure. I also don’t know any good source who has such an overview. That’s why I created a quick reference sheet of my own:
Feel free to download and use the PDF version: Telegram Structure.
Here is a source that I found particularly useful (besides some books): http://www.knx.org/fileadmin/template/documents/downloads_support_menu/KNX_tutor_seminar_page/tutor_documentation/05_Serial%20Data%20Transmission_E0808f.pdf
Please let me know if you’re missing some information or if you know of any good sources.