[comp.sys.ibm.pc] UART interrupt help needed !!

hb@vpnet.UUCP (hank barta) (02/05/90)

You didn't describe your hardware configuration, but if it
involves multiple serial I/O cards, the problem could be 
related to shared IRQ lines on the bus.

For example, COM1 and COM3 both use the same interrupt (IRQ4
if my memory serves me). Since DOS does not use these interrupts,
The board designers have not taken the trouble to insure that
one card can drive the line to its active state while the other
line is inactive. The line winds up somewhere in between and
and the interrupt controller may of may not recognize it. 

There are boards on the market that include four or eight ports
on one interrupt. If this is what you require, the "standard"
serial I/O cards may not work.

					Good Luck.
						hank