johnl@ima.UUCP (09/04/85)
I hardly believe this one. We're running DOS 3.1 on an XT, and have a program that sends stuff to an HP plotter which is hooked up at 9600 baud over a serial port. We're having strange problems setting the baud rate. If you use the MODE command to set the speed and send your bytes with DOS function 4, it works. Unfortunately, DOS is quite slow and we need to be able to use the second serial port, which DOS won't do. When we use the MODE command and send bytes directly through the BIOS, it doesn't work -- it seems like the baud rate hasn't been changed. When we set the baud rate ourselves, it works again. Has anybody ever seen this? How can the MODE command set the baud rate so that it affects DOS but not direct BIOS calls? It's hard to believe that DOS is going straight to the port and bypassing the BIOS. (The BIOS, by the way, provides no way to get the current baud rate, so it's unlikely that DOS is saving and restoring the speed.) Wisdom would be appreciated. John Levine, ima!johnl or Levine@YALE.ARPA