Compaq 850 manual Parallel Interface Control Registers, Address Register

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

		SPP	EPP	ECP
I/O		Mode	Mode	Mode
Address	Register	Ports	Ports	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

5-14Compaq Deskpro EXS and Workstation 300 Personal Computers

Featuring the Intel Pentium 4 Processor

First Edition – December 2000