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Chapter 5 Input/Output Interfaces
5.5.4.2 Parallel Interface Control
The BIOS function INT 17 provides simplified control of the parallel interface. Basic functions
such as initialization, character printing, and printer status are provide by subfunctions of INT 17.
The parallel interface is controllable by software through a set of I/O mapped registers. The
number and type of registers available depends on the mode used (SPP, EPP, or ECP). Table 5-11
lists the parallel registers and associated functions based on mode.
Table 5–11. Parallel Interface Control Registers
Table 5-11.
Parallel Interface Control Registers
I/O
Address
Register
SPP
Mode
Ports
EPP
Mode
Ports
ECP
Mode
Ports
Base Data LPT1,2,3 LPT1,2 LPT1,2,3
Base + 1h
Printer Status LPT1,2,3 LPT1,2 LPT1,2,3
Base + 2h Control LPT1,2,3 LPT1,2 LPT1,2,3
Base + 3h Address -- LPT1,2 --
Base + 4h Data Port 0 -- LPT1,2 --
Base + 5h Data Port 1 -- LPT1,2 --
Base + 6h Data Port 2 -- LPT1,2 --
Base + 7h Data Port 3 -- LPT1,2 --
Base + 400h Parallel Data FIFO -- -- LPT1,2,3
Base + 400h ECP Data FIFO -- -- LPT1,2,3
Base + 400h Test FIFO -- -- LPT1,2,3
Base + 400h Configuration Register A -- -- LPT1,2,3
Base + 401h Configuration Register B -- -- LPT1,2,3
Base + 402h Extended Control Register -- -- LPT1,2,3
Base Address:
LPT1 = 378h
LPT2 = 278h
LPT3 = 3BCh
5-14 Compaq Evo and Workstation Personal Computers
Featuring the Intel Pentium 4 Processor
Second Edition – January 2003