B&B Electronics Parallel Printer Card PIOC - Manual (Page 2)

Documentation Number PIOC2595 Manual 1
B&B Electronics -- PO Box 1040 -- Ottawa, IL 61350
PH (815) 433-5100 -- FAX (815) 433-5105
Overview
The Parallel Printer Card (Model PIOC) is a bi-directional
parallel port for a standard IBM PC or compatible. The PIOC is
single port card that can be used as a printer interface or as a
general input/output port for any device. The base port address of
the card can be set for any address from 0 to 3FC hexadecimal.
This allows the card to be located at the standard parallel port
addresses, as well as any other unused address.
The PIOC can have up to 12 digital TTL compatible outputs and
up to 17 digital TTL compatible inputs. 12 of these inputs and
outputs share connector pins so you cannot have 12 inputs and 17
outputs at the same time. The input/output lines are available
through a female DB-25 connector.
To understand how the PIOC can be used you must first
understand how the IBM PC parallel port works from inside the
computer. Each parallel port has one main port address for
outputting data, the Base Register. The next two addresses above
that address are used for handshaking control. The first address is
the Status Register, and the second address is the Control Register.
For instance, on a typical computer LPT1 might be located at
hexadecimal address 378h, which is the Base Register. The Status
Register will be located at 379h and the Control Register will be
located at 37Ah. Table 1 shows the functions of each pin on the DB-
25 connector when the PIOC is connected to a printer.