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PPIO2899 Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
There are three port addresses that are normally used on a PC
for parallel ports: 3BCH, 378H, and 278H. When your PC is reset or
turned on these three addresses are scanned by the BIOS in the
order shown above. The first one that the BIOS finds with a parallel
port installed is assigned the logical name LPT1. The second, LPT2,
etc. You can connect the PPIO to a port located at any of these
three addresses. During power up the computer will assign that port
a logical name but we will ignore it and communicate to the port
directly.
If you are using a base address of 0278H the I/O port addresses
in Table 1 would change to 0278H, 0279H, and 027AH. With a base
address of 03BCH the addresses are 03BCH, 03BDH, and 03BEH.
Check your computer manual to find out which address your parallel
port has. It is also possible to purchase a special parallel port from
B&B Electronics that can be set at any address in the I/O port
address space from 0000H to 03FFH.
The above parallel port information is true for the vast majority of
the PC compatible ports. However, a few computer manufacturers
have chosen to make their parallel ports non-standard. On some
battery powered computers pins are disabled to save power. Some
ports may also have extra “direction control” bits. If you have
problems where one or more bits are always on or off you should
check your owner's manual. You may have to enable the port or set
the “direction bit” correctly to get the port to work with the PPIO. If a
pin is missing you may have to install a different parallel port card to
get the PPIO to work properly.
