parallel port on a pc - c programming for ... -...

Parallel Port on a PC

Nick Urbanik

I/O Ports on a PC

Parallel Port in a PC

The Three Registers

Using the Printer Portfor General I/O

The pins on the 25-pinconnector

Permissions

Performing I/O inWindows XP, 2000, NT

Using Andy Eager’swrapper for logix4uinpout32.dll

References

License of thisDocument

Parallel Port on a PCC Programming for Engineers

Nick Urbanik [email protected]

This document Licensed under GPL—see slide 34

2005 October

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Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions



References


Outline

I/O Ports on a PCParallel Port in a PC

IntroductionThe Three Printer Port BaseAddresses

The Three RegistersThe Data PortThe Status PortThe Control Port

Using the Printer Port for GeneralI/OThe pins on the 25-pin connector

PermissionsPerforming I/O in Windows XP,2000, NTUsing Andy Eager’s wrapper forlogix4u inpout32.dll

Installing Andy Eager’swrapperUsing Andy Eager’s wrapperUsing inpout32.dll withoutAndy’s wrapper

ReferencesLicense of this Document

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I/O Ports on a PC


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Permissions



References


I/O Ports on a PC

I There are 216 = 65536 I/O addessesI each of these is called an I/O portI They are accessed with the in and out Intel assembly

language instructionsI The I/O ports are separate from ordinary memory

addressesI We say, “I/O ports have a separate address space from

memory addresses”.I I/O ports usually connect to registers on integrated circuits

on the motherboard or on cards plugged into themotherboard

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References


Hardware of I/O ports

I We cannot connect hardware directly to the data bus onthe CPU

I CPU may not source or sink enough currentI but the main reason is that the data bus is changing all the

timeI Carries instructions and other data, continuously passing

back and forthI For output: need a latch (set of flip-flops) to catch the data

when the output instruction is executed, and hold the datasteady

I For input: a tristate buffer (e.g., 571) that connects inputpin to data bus at the time the input instruction is executed

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Permissions



References


Hardware of Output Port

address

AEN

XIOW

address bus

data bus 8

16

8

decoder

octal latch

output port pins

to the outside world

D Q

I the latch “catches” the data and holds it when the outputinstruction is executed to the correct address

I The XIOW control line from the CPU’s control bus isactivated by the output instruction

I This keeps the I/O addresses separate from memoryaddresses even when they have the same addressnumber

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The Three Registers



Permissions



References


Hardware of Input Port

decoder

address16

8 8

address bus

XIOR

data bus

AEN

from the outside world

input port pins

I The tristate buffer connects the input pin to the data busonly when the input instruction is executed with theappropriate address

I The XIOR control line from the CPU’s control bus isactivated by the input instruction

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Nick Urbanik

I/O Ports on a PC

Parallel Port in a PCIntroduction

The Three Printer PortBase Addresses

The Three Registers



Permissions



References


Outline








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I/O Ports on a PC



The Three Registers



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References


Five modes of Operation

I Newer parallel ports are standardised under IEEEstandard 1284

I released in 1994I The standard defines five modes of operation:

Compatibility mode — sometimes called “CentronicsMode”

I can send data out onlyI upper limit: 50 kBps to 150 kBps, depending

on hardware

nibble mode Can input 4 bits at a timebyte mode can input a byte at a time using parallel

port’s bi-directional featureEPP mode (Enhanced Parallel Port) — Uses additional

hardware to perform handshakingECP Mode (Extended Capabilities Port) Uses DMA and

FIFO buffers to move data without using I/Oinstructions

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References


Handshaking with a printer in CompatibilityMode

To output a byte from the parallel port to the printer incompatibity mode:

1. Write the byte to the Data Port2. Check if the BUSY line is active

I If the printer is busy, the port will not accept any data, soany data sent to the data port will be lost

3. Take the STROBE line lowI Tells printer that valid data is waiting on the data pins 2–9

4. Put STROBE high again after about 5 microseconds.

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I/O Ports on a PC



The Three Registers



Permissions



References


Outline








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Nick Urbanik

I/O Ports on a PC



The Three Registers



Permissions



References


The Three Printer Port Base Addresses

Address Notes

0x3bc – 0x3bf Used for parallel ports that were incorporatedinto video cards, and now an option for anadditional port. Does not support ECP

0x378 – 0x37f Usual address for LPT1 (first parallel port)

0x278 – 0x27f Usual address for LPT2 (second parallel port)

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I/O Ports on a PC


The Three RegistersThe Data Port

The Status Port

The Control Port



Permissions



References


There are three I/O Ports

I Data portI At printer port base addressI all eight bits normally outputI Can input data if port has bi-directional hardware

I Status portI at base address + 1I read only

I Control PortI at base address + 2I read and write, though was originally intented as a write

only port.

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I/O Ports on a PC



The Status Port

The Control Port



Permissions



References


Outline








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Nick Urbanik

I/O Ports on a PC



The Status Port

The Control Port



Permissions



References


The Data Port

I At: base address of printer portI Write only, unless the port hardware is bi-directional

pin number Bit number signal name

2 bit 0 D0

3 bit 1 D1

4 bit 2 D2

5 bit 3 D3

6 bit 4 D4

7 bit 5 D5

8 bit 6 D6

9 bit 7 D7

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I/O Ports on a PC



The Status Port

The Control Port



Permissions



References


Outline








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I/O Ports on a PC



The Status Port

The Control Port



Permissions



References


The Status Port

I At: Base address + 1I Read only


bit 0 reserved

bit 1 reserved

bit 2 IRQ

15 bit 3 ERROR

13 bit 4 SLCT

12 bit 5 PE (Paper End)

10 bit 6 ACK

11 bit 7 BUSY

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The Status Port

The Control Port



Permissions



References


Outline








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I/O Ports on a PC



The Status Port

The Control Port



Permissions



References


The Control Port

I At: base address + 2I Read and Write


1 bit 0 STROBE

14 bit 1 AUTOFEED (Auto Linefeed)

16 bit 2 INIT PRN

17 bit 3 SELECT

bit 4 Enable IRQ via Ack

bit 5 Enable Bi-Directional Port

bit 6 Unused

bit 7 Unused

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References


Using the Printer Port for I/O

I Here, we use the printer port in compatibility modeI In this mode, the three ports are not available as general

purpose 8-bit input/output portsI They are set up to talk to a printerI But you can still use these ports for many purposes

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Signals and pin numbers for general purposeI/O

Port Signal Name DB25 pin number Comments

Data D0 2 All outputs latchedbase D1 3

D2 4D3 5D4 6D5 7D6 8D7 9

Status bit 3 ERROR 15 inputbase + 1 bit 4 SLCT 13 input

bit 5 PE 12 inputbit 6 ACK 10 inputbit 7 BUSY 11 inverted input

Control bit 0 STROBE 1 inverted outputbase + 2 bit 1 AUTOFEED 14 inverted output

bit 2 INIT PRN 16 outputbit 3 SELECT 17 inverted output

GND 18–25

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Pin numbers on DB25 Connector

I This views the female connectorI i.e., on the back of the computer

13 1

1425

12 11 10 9 8 7 5 4 3 2

24 23 22 21 20 19 18 17 16 15

6

View of female DB25 connector

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Pin Numbers on Parallel Port DB25Pin No(D-Type 25)

Pin No(Centronics)

SPP Signal Direction (Inor Out)

Register Inv?

1 1 STROBE In/Out Control Yes2 2 D0 Out Data3 3 D1 Out Data4 4 D2 Out Data5 5 D3 Out Data6 6 D4 Out Data7 7 D5 Out Data8 8 D6 Out Data9 9 D7 Out Data10 10 ACK In Status11 11 BUSY In Status Yes12 12 PE

(PaperEnd)In Status

13 13 SELECT In Status14 14 AUTOFEED

(Auto-Linefeed)In/Out Control Yes

15 32 ERROR /Fault

In Status

16 31 INIT PRN In/Out Control17 36 SELECT

Select-InIn/Out Control Yes

18 – 25 19 – 30 Ground GNDslide 22/34


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Permissions



References


Do not run your programs asroot/Administrator

I Normally, to access I/O ports requires administratorpriveleges

I . . . but it is a bad idea to do everything as the root oradministrative user

I A small mistake can stop the system from functioningcorrectly

I In Windows XP/2000/NT, additionally, special unsupportedsoftware is required.

I Linux provides a system call ioperm() that allows the rootuser to grant normal user access to particular ports

I The ports must be at port address 0x3ff or below

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References


Performing I/O in Windows XP, 2000, NTI Port I/O on Windows XP, Windows 2000, Windows NT is a

complex, barely supported mess.I Use Linux if you want something simple, standardised and

supported:http://linuxgazette.net/112/radcliffe.html

I Several people have built device drivers to work aroundthe limitations of Windows:

I inpout32.dll:http://www.logix4u.net/inpout32.htm

I PortTalk:http://www.beyondlogic.org/porttalk/porttalk.htm

I io.dll:http://www.geekhideout.com/iodll.shtml

I giveio.sys:http://www.physik.rwth-aachen.de/group/IIIphys/CMS/tracker/en/silicon/arcs_nt.html

I directio:http://www.direct-io.com/

I None of these are Open Source, but inpout32.dllseems to be best supported and have the most openlicense, so we will use that.slide 24/34

http://linuxgazette.net/112/radcliffe.html

http://www.logix4u.net/inpout32.htm

http://www.beyondlogic.org/porttalk/porttalk.htm

http://www.beyondlogic.org/porttalk/porttalk.htm

http://www.geekhideout.com/iodll.shtml

http://www.physik.rwth-aachen.de/group/IIIphys/CMS/tracker/en/silicon/arcs_nt.html

http://www.physik.rwth-aachen.de/group/IIIphys/CMS/tracker/en/silicon/arcs_nt.html

http://www.direct-io.com/


Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions


Using Andy Eager’swrapper for logix4uinpout32.dllInstalling Andy Eager’swrapper

Using Andy Eager’swrapper

Using inpout32.dll withoutAndy’s wrapper

References


Outline








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I/O Ports on a PC


The Three Registers



Permissions





References


Installing Andy Eager’s wrapper for logix4uinpout32.dll

Note: this is for use with Microsoft Windows. The procedurewith Linux is different, simpler and faster: see the references.

I Download Andy’s handy package fromhttp://www.linuxivr.com/c/week1/ioports.zip

I Unzip this into a temporary directoryI execute install.bat from a command prompt in that

directory as the Administrator

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http://www.linuxivr.com/c/week1/ioports.zip


Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions





References


Outline








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I/O Ports on a PC


The Three Registers



Permissions





References


Using Andy Eager’s wrapper

I See the program ledscan.c inhttp://www.linuxivr.com/c/week1/ioports.zip— use this as a model to see how to perform I/O

I Compile your program with the command:g++ -Wall -lioports -o 〈program〉〈program〉.cpp

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http://www.linuxivr.com/c/week1/ioports.zip


Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions





References


Outline








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I/O Ports on a PC


The Three Registers



Permissions





References


Using inpout32.dll without Andy’s wrapper

I This could (potentially) give better performance if youinitialise the library once at the beginning and free thelibrary once after all I/O is finished

I However, Andy says the difference in speed is notdetectable

See the test programhttp://www.hytherion.com/beattidp/comput/pport/test2.c, and also the source to Andy’s wrapperathttp://www.linuxivr.com/c/week1/install-io.html,and use them as a model for your program.

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http://www.hytherion.com/beattidp/comput/pport/test2.c

http://www.hytherion.com/beattidp/comput/pport/test2.c

http://www.linuxivr.com/c/week1/install-io.html

http://www.linuxivr.com/c/week1/install-io.html


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References


References — Web I

I logix4u.net.Inpout32.dll for WIN NT/2000/XP — logix4u.http://www.logix4u.net/inpout32.htm

Andrew Eager.Installing the logix4u IO interface.http://linuxivr.com/c/week1/install-io.html

logix4u.Parallel port Interfacing Tutorial.http://www.logix4u.net/parallelport1.htm

Joe D. Reeder.Controlling The Real World With Computershttp://learn-c.com/

Riku Saikkonen.Linux I/O port programming mini-HOWTOhttp://www.tldp.org/HOWTO/IO-Port-Programming.html

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http://www.logix4u.net/inpout32.htm

http://linuxivr.com/c/week1/install-io.html

http://www.logix4u.net/parallelport1.htm

http://learn-c.com/

http://www.tldp.org/HOWTO/IO-Port-Programming.html

http://www.tldp.org/HOWTO/IO-Port-Programming.html


Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions



References


References — Web II

P. J. Radcliffe.Linux: A Clear Winner for Hardware I/O.Linux Gazette, Issue 112, March 2005.http://linuxgazette.net/112/radcliffe.html

David Chong and Philip ChongLinux Analog to Digital Converter.Linux Gazette, Issue 118, September 2005.http://linuxgazette.net/118/chong.html

Craig PeacockInterfacing the Standard Parallel Port.http://www.beyondlogic.org/spp/parallel.htm

Jan Axelson.The PC’s Parallel Port.http://www.lvr.com/parport.htm

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http://linuxgazette.net/112/radcliffe.html

http://linuxgazette.net/118/chong.html

http://www.beyondlogic.org/spp/parallel.htm

http://www.lvr.com/parport.htm


Nick Urbanik

I/O Ports on a PC


The Three Registers



Permissions



References


References — Books

Steve Oualline.Practical C Programming.O’Reilly, 1993.

Paul Davies.The Indispensable Guide to C with EngineeringApplicationsAddison-Wesley, 1995.

Tom Adamson and James L. Antonakos and Kenneth C.Mansfield Jr.Structured C for Engineering and Technology, ThirdEdition.Prentice Hall, 1998.

Brian W. Kernighan and Dennis M. Ritchie.The C Programming Language.Prentice Hall, 1988.

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References


License covering this document

Copyright c© 2005, 2006 Nick Urbanik <[email protected]>You can redistribute modified or unmodified copies of thisdocument provided that this copyright notice and thispermission notice are preserved on all copies under the termsof the GNU General Public License as published by the FreeSoftware Foundation — either version 2 of the License or (atyour option) any later version.

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