HP Vectra Technical Reference Manual page 227

Table 7.1
Serial and Parallel Port Addresses
I/O Address
3F8H
2F8H
3E8H
2E8H
3BCH
378H
278H
IRQ
4
3
10
11
5
7
INT
OCH
OBH
72H
73H
OOH
OFH
Port addresses are added to the base port address tables in the sequence listed in table 7.1 . If the
system has only two parallel I/O ports at addresses 378H and 278H then 378H becomes the first
entry in the table (Port 0) and 278H becomes the second (Port
1).
The potential parallel port at
3BCH would not be Port 0 as it is not present in the system.
The functions supported by the serial and parallel port drivers rely on the values contained in the
serial base port address table and the parallel base port address table. The ports are referenced
~
by -indexes into the tables (port numbers 0-3).
7.1.2 Print Screen Driver
The print screen driver provides a simple method for application programs and system software
to print a copy of the screen contents to the system printer (port 0). The ROM BIOS print screen
driver will only print the scr,een if the display adapter is in one of the alphanumeric modes.
Support for printing the screen when in graphics modes is provided by the DOS command
GRAPHICS.
218 Serial and Parrallel I/O