[comp.sys.ibm.pc] Programming the serial port: 2 questions

cjdb@tank.uchicago.edu (Charles Blair) (08/15/89)

Let me see if I can state this clearly.

I'm working on a communications program that self-configures according to which
serial port address it finds at 0000:0400. On the particular machine I'm
developing on, the address if finds there is 02F8, in other words, COM2.
However, when I initialize the serial port using int 14h, it seems I must
initialize COM1 (dx=0) for the port to be initialized properly. Why is this?
If the BIOS finds only one serial port, does it consider this to be COM1
regardless of its address?

On an unrelated note, I want to redirect printer output from a
parallel port to the serial port. The Shift PrtScreen interrupt is
already grabbed by my code. What is the best way to do this (i.e.,
emulate the function of the DOS mode command redirecting output from
LPT1 to COM1)?

Any help would be appreciated. E-mail preferred, as I do not regularly read
this group. Thanks.

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