C parallel port [Compatibility Mode].pdf

7/27/2019 C parallel port [Compatibility Mode].pdf

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© Dr J.Iqbal



Port

• A port is a set of signal lines that the

micro rocessor or CPU uses to exchan e data

with other components.•

printers, modems, keyboards and display. Most

is 0 or 1.

© Dr J.Iqbal



Parallel Port Vs Serial Port• A parallel port sends and receives data eight bits

.

to be transferred very quickly; however, the

number of individual wires it contain.

• A serial ort sends and receives data one bit at

a time over one wire. While it takes eight times

as long to transfer each byte of data this way,

only a few wires are required.

© Dr J.Iqbal



Serial Vs Parallel Data

© Dr J.Iqbal



Comparison• Serial and Parallel

• 8 bits can be send at a• 1 bit can be send at a

t me

• Fast data transfer

t me

• Slow data transfer

for ground is required

• More components,

for ground is required

• less components, less

more chances of failure

• More cost

chances of failure

• Less cost

© Dr J.Iqbal



Parallel port

© Dr J.Iqbal



PortThe original IBM-PC's Parallel Printer Port had a

total of 12 digital outputs and 5 digital inputs

• 8 out ut ins accessed via the DATA Port

• 5 input pins (one inverted) accessed via the STATUS Port

• 4 output pins (three inverted) accessed via the CONTROL Port

© Dr J.Iqbal



I/O Ports Address

Address Description

From Until

000 00F DMA Controller (direct memory access)

020 02F Master Interrupts

030 03F Slave Interrupts

040 043 Timer

060 060 Keyboard

pea er

170 17F First disk drive

200 20F Game Port

2E8 2EF Serial Port 4 COM4

2F8 2FF Serial Port 2 COM2

378 37F Second parallel port LPT2

3B0 3BB Monochromevideo adapter

3BC 3BF First parallel port LPT1

3E0 3EF Serial port 3 COM3

© Dr J.Iqbal

3F8 3FF Serial port 1 COM1

220 22F Usually used by sound cards



Address of parallel port in windows

• Control panel

•

• OR right click – my computer and then properties

• Device manager

•

• Parallel port (right click, then click properties)

• esources rea a ress o e para e por

© Dr J.Iqbal



Address of parallel port in DOS

• c:\> debug <press enter>

-

• _________________________________________

Microsoft Windows 2000 [Version 5.00.2195]

(C) Copyright 1985-1999 Microsoft Corp.

-d 0040:0008

0040:0000 BC 03 78 03 78 02 C0 9F ..x.x...

0040:0010 23 C8 FE 80 02 92 10 20-00 00 36 00 36 00 64 20 #...... ..6.6.d

0040:0020 20 39 30 0B 30 0B 34 05-30 0B 3A 27 30 0B 30 0B 90.0.4.0.:'0.0.0040:0030 30 0B 38 09 0D 1C 00 00-00 00 00 00 00 00 00 00 0.8.............

0040:0040 F9 00 C3 00 00 00 00 00-00 03 50 00 E0 1F 00 00 ..........P.....

-

© Dr J.Iqbal

................

0040:0060 07 06 00 D4 03 29 30 80-02 00 18 00 B1 62 0D 00 .....)0......b..

0040:0070 00 00 00 00 00 00 08 00-14 14 14 14 01 01 01 01 ................0040:0080 1E 00 3E 00 31 08 00 60



Parallel port• Data Port

• Status Port

• Control Port

© Dr J.Iqbal(Note that the S7, C0, C1 & C3 signals are inverted)



Parallel Port Address

Address Port Name Read/Write

ase a a or r e

Base + 1 Status Port Read

Base + 2 Control Port Write

378H PORT: In this address the CPU writes the data to be sent to the printer.

It is an OUTPUT port. The eight data bits (D0-D7) are latched to appear in the

output connector.

379H PORT: This is an INPUT port. These signals are used by the CPU to

37AH PORT: In this port the computer writes the signals that control the

printer. Therefore, it is an OUTPUT port.

© Dr J.Iqbal



Pin Assignment used by Printer

Pin Signal IN/OUT Function

1 Strobe Out A low on this line indicates data is

ready

2-9 Data 0-7 Out Data Bus.

10 Ack InInterrupt Line. tells computer that data

has been received.

11 Busy In

Used when buffer is full. A high signal

asserted by the printer to indicate that it

is busy and cannot take data.

12 Paper Out In Communicate paper out

13 Select In High means printer is online/present

14 Auto Linefeed Out Advance a er

15 Error / Fault In Error has occurred

16 Init Out Reset - Active Low

© Dr J.Iqbal

17 Select Printer Out.

printer that it is selected.

18-25 Ground GND Ground



Output

STROBE/: (C0) Tells the printer when the eight data bits are ready to be read. Turns to a

low logic level when the data are ready.

AUTO FD/: (C1) Tells the printer to advance paper.

INIT/: (C2) Reset the printer.

SLCT IN/: (C3) Used to indicate to the printer that it is selected.

- : ata ts.

Inputs:

: n error as occurre . e s op sen ng more a a

SLCT: (S4) Tells the computer that a printer is present.

PE: S5 The rinter is out of a er.

ACK/: (S6) Tells the CPU that the data has been correctly received.

BUSY: (S7) The printer sets this line when its buffer is full. The computer will stop sending

© Dr J.Iqbal

more data.



Addressing the port

Data Bits Table

BIT FUNCTION PIN

D0 data 0 2

Status Bits Table

BIT FUNCTION PIN

D0 not used

Control Bits Table

BIT FUNCTION PIN

D0 STROBE 1

D1 data 1 3

D2 data 2 4

D1 not used

D2 not used

D1 AUTO FD 14

D2 INIT/ 16

D4 data 4 6

D5 data 5 7

D4 SLCT/ 13

D5 PE 12

D4 Not used

D5 not used

D6 data 6 8D7 data 7 9

D6 ACK/ 10D7 BUSY/ 11

D6 not usedD7 not used

© Dr J.Iqbal(Note that the pins 1, 10, 14, 17 are inverted)



#i ncl ude <st di o. h>#i ncl ude <dos. h>

.

/ *Thi s pr ogr am set t he

send a byte to the parallel port

output addresses. It's as easy

par a e por t

out put s*/

as you can see. e ou por ;

function sends a byte to aspecified I/O port. The first

voi d mai n ( voi d){cl r scr ( ) ;

function parameter is the

address of the port to write a

,get ch( ) ;

}

.

the value of the byte to send.

Both parameters can be defined

.

© Dr J.Iqbal




< .

/ *Thi s pr ogr am set t he par al l el

or t out ut s*/

voi d mai n ( voi d){unsi gned i nt BaseAddr ess=0x378;

cl r scr ( ) ;out por t b( BaseAddr ess+2, 0xf f ) ;

get ch( ) ;}

ove program s ows ow o sen a y e o e on ro por of parallel port. Control port is at Base+2 address. Remember

that bit 0,1,3 of control port was inverted by hardware. To get

© Dr J.Iqbal

correct result, we need to use exclusive OR with 0xb [1011],

which will give us correct result.



Problem

, , o con ro por was nver e y

hardware. To get correct result, we need to do

some man pu a on. a are ose

© Dr J.Iqbal




< .

/ *Thi s pr ogr am set t he par al l el

or t out ut s*/

voi d mai n ( voi d){unsi gned i nt BaseAddr ess=0x378;

cl r scr ( ) ;out por t b( BaseAddr ess+2, 0xf f 0̂xb) ;

get ch( ) ;}

ove program s ows ow o sen a y e o e on ro por of parallel port. Control port is at Base+2 address. Remember

that bit 0,1,3 of control port was inverted by hardware. To get

© Dr J.Iqbal

correct result, we need to use exclusive OR with 0xb [1011],

which will give us correct result.



#include <stdio.h>

#include <dos.h>

#include <conio.h>

/*This function read parallel

port inputs*/

to read a byte from

the arallel ort in ut

int Read_Input(){int Byte;

Byte=inportb(0x379);

address.The main function is only

return Byte;

}

void main void

used to show the

value of the byte on the

{int PP_Input;

clrscr();

PP In ut = Read In ut

.

The inportb(); function

read a b te from the _ _

printf("%d",PP_Input);getch();

}

specified I/O address of

the computer.

© Dr J.Iqbal



Pin SPP Signal EPP Signal IN/OUT Function

A low on this

1 Strobe Write Out

line indicates a

Write, High

indicates a

2-9 Data 0-7 Data 0-7 In-Out Data Bus. Bi-directional

10 Ack Interrupt In Interrupt Line.

11 Bus Wait In

Used for

handshaking.

A EPP cycle

can be started

when low, andfinished when

high.

© Dr J.Iqbal

12Paper Out /

EndSpare In

Spare - Not

Used in EPP

Handshake



Spare - Not

Pin SPP Signal EPP Signal IN/OUT Function

13 Select Spare In Used in EPP

Handshake

When Low,

transfer

15 Error / Fault Spare In

Spare - Note

used in EPP

an s a e

16 Initialize Reset OutReset - Active

Low

17 Select Printer Address Strobe Out

When low,

indicates

Address transfer

18-25 Ground Ground GND Ground

© Dr J.Iqbal

C parallel port [Compatibility Mode].pdf

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