Parallel Programming Tutorial

Parallel Port

In 1284, the IEEE 1994 standard defined five parallel transmission modes:

1) compatibility mode

2) nibble Mode

3) byte mode

4) EPP enhanced parallel port Mode

5) ECP Extended Parallel Port

The hardware connector of the parallel port is db25, which is divided into three groups, such

 

1) Data lines (Data Bus) data lines
2) control lines
3) status lines
The data line is used to transmit data. The control line is used to control peripheral devices. The peripheral devices return status signals through status lines. These lines are connected to internal data registers, control registers, and status registers respectively.

The signal of the db25 pin is as follows:

Pin no (db25)	Signal name	Direction	Register-bit	Inverted
1	Nstrobe	Out	Control-0	Yes
2	Data0	In/out	Data-0	No
3	Data1	In/out	Data-1	No
4	Data2	In/out	Data-2	No
5	Data3	In/out	Data-3	No
6	Data4	In/out	Data-4	No
7	Data5	In/out	Data-5	No
8	Data6	In/out	Data-6	No
9	Data7	In/out	Data-7	No
10	Nack	In	Status-6	No
11	Busy	In	Status-7	Yes
12	Paper-out	In	Status-5	No
13	Select	In	Status-4	No
14	Linefeed	Out	Control-1	Yes
15	Nerror	In	Status-3	No
16	Ninitialize	Out	Control-2	No
17	Nselect-printer	Out	Control-3	Yes
18-25	Ground	-	-	-

Parallel register:

The data, control, and status lines are connected to the registers that match the computer's internal systems. Therefore, you can program these registers and read and write them through the 'C' or 'basic 'language.

Standard parallel port registers include:

1) Data Register data register
2) Status Register
3) control register

By writing these registers, the corresponding voltage signals will be transmitted online, which can be measured by a multimeter. The signals sent to the parallel port can also be read through these registers, for example: we write "1" to the data register, and data0 will be raised to + 5 V voltage, so that we can open or close the data line or control line through programming.

 

Where are these registers?

In ibm pc, these registers are Io ing and are unique addresses. On a typical PC, the base address of LPT1 is 0x378, and the base address of lpt2 is 0x278, the base address of lpt3 is 0x3bc.

The data register is on the base address, and the Status Register is on the base address + 1. The control register is on the base address + 2. Therefore, once we know the base address, we can calculate the address of other registers.

Register	LPT1	Lpt2	Lpt3
Data registar (baseaddress + 0)	Zero X 378	Zero X 278	0x3bc
Status Register (baseaddress + 1)	Zero x 379	Zero x 279	0x3bd
Control Register (baseaddress + 2)	0x37a	0x27a	0x3be

Programming specifications:

Almost all programming languages provide database functions to access the parallel port. For example, Borland C provides the "inportb" and "outportb" functions to read or write the IO ing addresses of external devices. This tutorial provides examples of VC, but it is easy to transplant to other compilers such as Borland C and TC. VB does not directly provide an access function for the parallel port, but it can be easily added through DLL. VC provides two functions to access the IO ing of the peripheral device, and read "_ indium, "_ outp" is written. These functions are declared in "conio. H.

Simple hardware testing program:

VC ++ example:

Step 1: Create a project:

 

 

 

Enter the code in example. cpp after clicking finish:

 

# Include "stdafx. H"

# Include "conio. H"

# Include "stdio. H"

# Include "string. H"

# Include "stdlib. H"

 

Int main (INT argc, char * argv [])

{

Short data;

 

If (argc <2)

{

Printf ("usage/n ");

Printf ("partest1.exe,/n ");

Return 0;

}

If (! Strcmp (argv [1], "read "))

{

Data = _ Indium (atoi (argv [2]);

Printf ("data read from parallel port is ");

Printf ("% d/n", data );

}

If (! Strcmp (argv [1], "write "))

{

_ Outp (atoi (argv [2]), atoi (argv [3]);

Printf ("data written to parallel port is ");

Printf ("% s/n", argv [3]);

}

Return 0;

}

Compile this program and copy it to "C :/"

How to test the program?

Connect the hardware, open the command prompt box, switch to C: input: partest1.exe write 888 press enter, if all are correct, then the LED1-LED8 will shine, Here 255 is 0x888, that is, the base address (data register) of lpt1 ). 255 is the data written into the data register. If the "partest1 read 888" program is input, the value of the data register will be read from the parallel port and displayed.

From: http://blog.csdn.net/lqrensn/article/details/5654708