Compaq W4000 Manual De Usuario

Chapter 5  Input/Output Interfaces 

 
 

 
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 

 

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