Somewhat confused with Interrupts/TSRs

[John Coppens <john@jcoppens.com>]

Hello people.

I accepted the task of trying to get a very old datalogging program
working for a friend. It is needed to read an older sensor, and
apparently no other software is available.

It's a bit large (170 kB exe) to disassemble completely, but cursory
investigation shows it was written in Turbo Pascal. Apparently the CRT
unit was included, which makes executable use internal keyboard access
instead of MsDOS functions.

All this is important, because I want to simulate keypresses and the TSR
doesn't seem to work with any CRT using Pascal program.

I followed the program to be using Int16 for key input, which probably
explains why no Int28 or Int1C calls are made anymore (needed for the
TSR to work)...

I tried to follow where 16h goes to, but, using debug in DOSemu, this
leads to a HLT instruction...

Does anyone know of this (TSR) problem or can anyone suggest a solution?

Thanks!
John