By Ulrich Günther DL1NDB/ZL1DDL
For many users, especially outside Germany, "BayCom" is synonymous with the 1200Bd modem for the serial (RS-232) port - or one of its many homebrew and other derivates that have been developed.
Many users have contacted the BayCom team and its representatives about problems that they experienced running their BayCom modem under Windows 3.0, 3.1 or 95/98.
This problem comes as no surprise. The BayCom terminal software was developed to run under DOS. While the software itself will generally run under Windows, it is the operating system that causes the trouble.
Why? Well, the BayCom RS-232 modems all operate on the same principle: incoming data is converted from audio tones to a bit stream. This bit stream is handed to the serial port, which generates an interrupt to handle incoming bits.
This interrupt is time-critical and needs to be attended to by the software immediately after it is received. This is easy as long as the interrupt is handed straight to L2. And this is where the problem creeps in: Windows (and other multitasking systems) prefer to take care of the interrupt themselves, and kick L2 into action when it suits them. As a result, L2 may receive the interrupt too late - which from L2's point of view means that it "sees" a bitstream different from the one that was actually received.
This is only a problem for RS-232 modems - USCC cards and parallel port modems will usually run nicely even under Windows. On some Windows machines, even the serial modem will run satisfactorily. If yours is one of them, enjoy it while it lasts - but please don't tell the
As of recently, a program by George SV2AGW has become available that overcomes this problem. Other programs that do this are Winpack, Jon G7JJF's WinTNC, and of course the SER12 driver for FlexNet.