IBM 3270 controller emulation

On Dec 8, 2017, at 5:22 PM, Charles Anthony via cctalk <cctalk at classiccmp.org> wrote: I am trying to wire 3270 support into the DPS8/M emulator. Multics supports 3270 via a bisync connection to the 3270 controller. Multics sends commands to the Front End Network processor, which (originally) passed the commands down the bisync line to the 3270. I have a running Multics and running 3270 display emulators using tn3270 (3270 over telnet), so I need to write the code that maps the Multics commands into 3270 controller commands (and vice versa) and manages the telnet connections to the 3270 display emulators and maps the tn3270 traffic into 3270 controllers. I don't need to actually implement the bisync communications; the controller emulator will be running inside the FNP emulator, but I need to express controller responses to Multics in the bisync format, as Multics is expecting that the responses arrived over a bisync connection. The problem is that I have no idea how the 3270 controllers worked; I've looked through the bitsavers collection; those documents are largely concerned with the displays and tend to treat the controllers as 'black boxes' that just do the right thing. So I am seeking pointers to documentation that will give me a better grasp of the controller functionality and/or discussions with someone who knows how they work..... Thanks, -- Charles