well, sort of http://www.barrcentral.com/support/documents/manuals/3270%20for%20RJE% 2094%20Manual.pdf Is a product manual for a DOS product that could simulate the establishment controller and the terminal, so it has a nice overview of the whole path back to the mainframe. It was enough to answer most of my questions about where to look for more detailed information if I ever need to know..