Solution:

Yes, the PC-ComLIB dose support the share IRQ function. But since the DOS is not a multi-task OS, we can not set all ports to the same interrupt service routine, if we do so, the system will have difficulty in judging from which port comes the interrupt . There are two way to solve it: 1, Assign the ports to the different service routine, and you will know which port is working if the corresponding service routine is called. 2, Read the vector register yourselves in the unique service routine, and you can also know the interrupt statue. It will be no problem to operate the ports which are sharing IRQ with each other by following this principle.