The /p switch has no meaning and is ignored.
The valid switches are:
/c:xx where xx is the COM port
/b:xx where xx is the baud rate
/I:xx where xx is the IRQ (/I must be uppercase)
For instance, typing
PCCOM /c:2 /b:9600 /I:3
will invoke PCCOM using COM port 2, IRQ level 3, and 9600 baud
I think the IR port is COM3, but that's off the top of my head. I suggest that you verify that rather than take my word for it.
Steve