SimH PDP-8 ttox device help

I've been attempting to interface with SimH in the least invasive way possible, by connecting two programs together via a pseudo-TTY created by socat connected to one of the telnet ports of a TTIX device. Something like this: TTIX -> telnet port -> socat -> /dev/ttyPDP (pty) This works fine for the console port. I personally like having minicom pulled up for the serial terminal but keep the other window cluttered with SimH backend commands. I have been able to manipulate EDIT.SV with a simple C program to transfer text files, character by character, which is neat. I wanted to extend this to a VC8-E emulator, again in the simplest way possible. I am sending out the X- and Y-coordinates for the point over TTOX0, but seem to be encountering some problems. I noticed that it likes to get hung up on a TSF (6411) instruction, causing it to keep looping even in single-step mode! Assuming everything is buffered, I would be under the assumption that TSF would almost always skip with a successful device send. [...] Step expired, PC: 00313 (IOT 411) \ a lot more of these (~50) Step expired, PC: 00314 (JMP 313) / Step expired, PC: 00313 (IOT 411) Step expired, PC: 00314 (JMP 313) Step expired, PC: 00313 (IOT 411) Step expired, PC: 00314 (JMP 313) Step expired, PC: 00313 (IOT 411) Step expired, PC: 00315 (IOT 416) <- finally skips! By the way, I am initializing the device with a CLA; TLS (6416) at the beginning of the program. I noticed David Gesswein opened up a somewhat related issue, now marked as closed, in October 2013. https://github.com/simh/simh/issues/85 Once I'm back to the real hardware, I intend to try it there to verify. I am running V3.9-0, by the way. Any insight into what might be holding TSF up would be much appreciated. Thanks, Kyle