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Parallel port - LPT (IEEE 1284)

Antonín Vojáček, 15. April 2007 - 0:00

Summary of required information, tutorials, instructions, tips & tricks, datasheets etc

Content


Introduction

Parallel port LPT is the standard component in all common personal computers for parallel data communication (parallel bits transfer) by 17 digital lines, which can be divided on 8 data signal lines and 9 lines for communication control (hanshaking). A PC with a peripherial device can be interconnected by 2m long cabel for certainty, but in practise it is usually possible to use up to 5m long cabel.

The parallel port for the PC was originally made for communication with a printer, it means one direction data transfer. Later it was specified other modes which modify LPT port for bidirectional data transfer with data rate up to 5Mbps. The parallel port was standardized in 1997 as IEEE 1284. This standard defines 5 activity modes:

    1. SPP mode - Compatibility Mode (Centronics mode).
    2. Nibble Mode.
    3. Byte Mode.
    4. EPP Mode (Enhanced Parallel Port).
    5. ECP Mode (Extended Capabilities Mode).

LPT port connection

Parallel port usually uses two types of connectors:

  • 25 pin D-sub female conector (figure 1), which is usually part of a PC motherboard.
  • 36 pin Centronics female conector, which is usually used in printers and others peripheral devices.

In figure 1., there is description of each pin and signal, which represents them. There is pertinence each pin to PC register (Data,Status, Control) for both connectors. Standard IEEE1284 defines also 36-pin connector similar with Centronics, but smaller.

Fig. 1. LPT signals assigment to 25-pin D-SUB connector

 

Pin No (D-Type 25)

Pin No (Centronics)

SPP Signal

Direction In/out

Register
Hardware Inverted
1
1
nStrobe
In/Out
Control
Yes
2
2
Data 0
Out
Data
 
3
3
Data 1
Out
Data
 
4
4
Data 2
Out
Data
 
5
5
Data 3
Out
Data
 
6
6
Data 4
Out
Data
 
7
7
Data 5
Out
Data
 
8
8
Data 6
Out
Data
 
9
9
Data 7
Out
Data
 
10
10
nAck
In
Status
 
11
11
Busy
In
Status
Yes
12
12
Paper-Out / Paper-End
In
Status
 
13
13
Select
In
Status
 
14
14
nAuto-Linefeed
In/Out
Control
Yes
15
32
nError / nFault
In
Status
 
16
31
nInitialize
In/Out
Control
 
17
36
nSelect-Printer / nSelect-In
In/Out
Control
Yes
18 - 25
19-30
Ground
Gnd
 
 

Tab 1. Pin Assignments of the D-Type 25 pin Parallel Port Connector

Note: Pins table for LPT with their names is possible to download in Documents section or with figures of Centronics port pins resolution in LPT port pins resolution for IEEE 1284 standard.

Signals definition

Output signals of the parallel port are defined as typical TTL logical level signals. High level is defined by voltage from 3.5V to 5.5V and low level from 0V to 0.4V (figure 2.).

Diferent values of maximal load currents of the parallel port are done by physical realization of the port. Maximal current takes from pins should be from range 4mA and 20mA. Therefore it's better use a buffer between PC and peripheral device.

Fig. 2. TTL voltage level definition (input voltage, output voltage)

 
Rules for safe work against port destruction PC port addresses

In comparison with serial port the parallel port can be destroyed very easily, because outputs aren't usually protected against overload and overcharge. Therefore it's better to keep following precautions:

  • Devices should be connected only to switch off power supplies of computers.
  • At inputs there should be brought only voltage betwen 0 and 5V.
  • Outputs should make short circuit or should be connected to others outputs.
  • Outputs should be contacted with strange voltage.
  • In work with parallel port should be kept all outlines for minimalization of static electricity.

For PC parallel ports it's defined and used 3 basic addresses which show table 2.

Address
Notes:

3BCh - 3BFh

 Used for Parallel Ports which were incorporated on to Video Cards - Doesn't support ECP addresses
378h - 37Fh
 Usual Address For LPT 1
278h - 27Fh
 Usual Address For LPT 2
Tab 2. Table 2 Port Addresses

Address 3BCh was originally used for old Video cards and nowadays it isn't used. In BIOS there can be found port addresses in memory accirding to table 3.

Start Address

Function
0000:0408
 LPT1's Base Address
0000:040A
 LPT2's Base Address
0000:040C
 LPT3's Base Address
0000:040E
 LPT4's Base Address (Note 1)
Tab 3. Adresy LPT portů v datové oblasti BIOSu

Linkage of mostly used cabels

Tiskový kabel (Centronic)
Použití: připojení tiskárny k LPT portu.

Redukce Centronic - LapLink
Použití: spojení dvou PC tiskovým kabelem (Centronic) jako LapLinkovým
LapLink kabel
Použití: propojení dvou PC


25 pin D-sub connector
(into PC )
 

36 pin Centornics connector
(into printer)

Name
 25-DSub 36-Cen
Strobe
1
1
Data Bit 0
2
2
Data Bit 1
3
3
Data Bit 2
4
4
Data Bit 3
5
5
Data Bit 4
6
6
Data Bit 5
7
7
Data Bit 6
8
8
Data Bit 7
9
9
Acknowledge
10
10
Busy
11
11
Paper Out
12
12
Select
13
13
Autofeed
14
14
Error
15
32
Reset
16
31
Select
17
36
Signal Ground
18
33
Signal Ground
19
19,20
Signal Ground
20
21,22
Signal Ground
21
23,24
Signal Ground
22
25,26
Signal Ground
23
27
Signal Ground
24
28,29
Signal Ground
25
30,16
Shield
Shield
Shield+17

Pro zvětšení kliknětě na obrázekj

For higher resolution click on the figure


36 pin Centornics connector
(into printer cabel from PC 1)
 

25 pin D-sub connector
(into PC 2)
 
Name Cen DSub Name
Data Bit 0
2
15
 Error
Data Bit 1
3
13
 Select
Data Bit 2
4
12
 Paper Out
Data Bit 3
5
10
 Acknowledge
Data Bit 4
6
11
 Busy
Acknowledge
10
5
 Data Bit 3
Busy
11
6
 Data Bit 4
Paper Out
12
4
 Data Bit 2
Select
13
3
 Data Bit 1
Error
32
2
 Data Bit 0
Reset
16
16
 Reset
Select
17
17
 Select
Signal Ground
19-30+33
18-25
 Signal Ground


25 pin D-sub connector
(into PC 1)
 

25 pin D-sub connector
(into PC 2)

Name Pin Pin Name
Data Bit 0
2
15
 Error
Data Bit 1
3
13
 Select
Data Bit 2
4
12
 Paper Out
Data Bit 3
5
10
 Acknowledge
Data Bit 4
6
11
 Busy
Acknowledge
10
5
 Data Bit 3
Busy
11
6
 Data Bit 4
Paper Out
12
4
 Data Bit 2
Select
13
3
 Data Bit 1
Error
15
2
 Data Bit 0
Reset
16
16
 Reset
Select
17
17
 Select
Signal Ground
25
25
 Signal Ground

For higher resolution click on the figure

Rules for making communication cables

For an every data cabel and for parallel cabels two-times important is shielding. Every data line should has its ground line (GND) side by side or should be shielded. So it's possible to avoid crosstalks between lines. It means possible higher data rate and communication on further distance. If a flat cabel is used, the wiring will be done by structure of the cabel and port. If wires budle is used, every data line should be twisted with signal ground line. Shielding of all twisted pairs makes the parameters better.

LPT communication modes

SPP Mode - Compatibility Mode

This mode is also called Centronics mode and it is standard mode for parallel data communication. It was originally intended only for communication PC with printer. There is defined only forward data transfer, it means from a PC to a peripheral device and data rate can be only to 150kbps. Communication process is described in following figure 3.

Fig. 3. Compatibility Mode (SPP mode) Data Transfer Cycle

Compatibility Mode phase transitions:

  1. Write the data to the data register
  2. Program reads the status register to check that the printer is not BUSY
  3. If not BUSY, then Write to the Control Register to assert the STROBE line
  4. Write to the Control register to de-assert the STROBE line 

In nowadays, many of the integrated 1284 I/O controllers have implemented Fast Centronics or Paralel Port FIFO Mode, which use FIFO buffers for data transfer. Then data written in FIFO port are transfered to printer using hardware generated handshake signals and it increases data rate up to 500KBbs. However this mode isn't defined in standard IEEE 1284.

SPP Register Interface

The basic SPP mode of parallel port is controled by 3 base registers:

  • Data Register - intended for writing of transmit data určený pro zápis vysílaných dat
  • Status Register - intended for reading states on the lines.
  • Control Register - intended for controlling of the peripherial device, which receives transmitted data.

Pins allocation to bits in registers is in the following figure 4.

 

Fig. 4. Bits allocation in the LPT parallel port

    Offset
    Name
    Read/Write

    Bit No.

    Properties
    Base + 0
    Data Port
    Write
    Bit 7
    Data 7
    Bit 6
    Data 6
    Bit 5
    Data 5
    Bit 4
    Data 4
    Bit 3
    Data 3
    Bit 2
    Data 2
    Bit 1
    Data 1
    Bit 0
    Data 0

    Tab 4. Data Register

    On base address there is data register for transmitting of the 8-bit value on lines. The register is intended only for writing. Reading is possible, but it is read only last transmited byte.  

Offset
Name
Read/Write

Bit No.

Properties
Base + 1
Status Port
Read Only
Bit 7
Busy
Bit 6
Ack
Bit 5
Paper Out
Bit 4
Select In
Bit 3
Error
Bit 2
IRQ (Not)
Bit 1
Reserved
Bit 0
Reserved

Tab. 5. Status Register

Status register with address base +1 is intended for reading and describes state of the communicating device (printer).

Offset
Name
Read/Write

Bit No.

Properties
Base + 2
Control Port
Read/Write
Bit 7
Unused
Bit 6
Unused
Bit 5
Enable Bi-Directional Port
Bit 4
Enable IRQ Via Ack Line
Bit 3
Select Printer
Bit 2
Initialize Printer (Reset)
Bit 1
Auto Linefeed
Bit 0
Strobe

Tab. 6. Control Register

Control register (Tab. 6) is designated for writing and it enables to control of communicating device (printer) by the 5 output bits.

Nibble Mode

Nibble mode is way how to get reverse channel and bidirectional communication between peripherial device and PC directly from classical SPP Compatible mode without hardware adjustment. It is neccesary only software support. Therefore the data rate limit is up to 100kbps. The advantage is ability of bidirectional communication on all PCs with LPT.

For transfer it is used 5 inputs lines of PC port which are intended for the handshake. The four ones are used for data transfer into PC. Using of these lines the periphery can transmit byte as sequence of 2 nibbles (4 bits) in two followings data cycles. Both cycles decribe figure 5. and table 7.

 

Fig. 5. Byte Mode Data Transfer Cycle

SPP Signal Nibble Mode Name In/Out Description -- Signal usage when in Nibble Mode data transfer
nSTROBE nSTROBE Out Not used for reverse data transfer
nAUTOFEED HostBusy Out Host nibble mode handshake signal. Set low to indicate host is ready for nibble. Set high to indicate nibble has been received.
nSELECTIN 1284Active Out Set high when host is in a 1284 transfer mode.
nINIT nINIT Out Not used for reverse data transfer
nACK PtrClk In Set low to indicate valid nibble data, set high in response to HostBusy going high.
BUSY PtrBusy In Used for Data bit 3, then 7
PE AckDataReq In Used for Data bit 2, then 6
SELECT Xflag In Used for Data bit 1, then 5
nERROR nDataAvail In Used for Data bit 0, then 4
DATA[8:1] Not Used    

Tab. 7. Nibble Mode Signals

Byte Mode

After implementation of parallel port interface, some producers in the lead with IBM increase transfer capacity by removing data lines drivers and provide bidirectional 8-bit communication by way of data lines. Then data rate is up to 200kbps. Figure 6. shows one transfer cycle in this mode and table 8. describe particular signals.

 


Fig. 6. Časový průběh komunikace v obousněrném Byte módu

SPP Signal Byte Mode Name In/Out

Description
Signal usage when in Byte Mode data transfer

nSTROBE HostClk Out Pulsed low at the end of each Byte mode data transfer to indicate that the byte was received. Acknowledge signal.
nAUTOFEED HostBusy Out Set low to indicate host is ready for byte. Set high to indicate byte has been received. Handshake signal.
nSELECTIN 1284Active Out Set high when host is in a 1284 transfer mode.
nINIT nINIT Out Not used. Set high.
nACK PtrClk In Set low to indicate valid data on the data lines, set high in response to HostBusy going high.
BUSY PtrBusy In Forward channel Busy status.
PE AckDataReq In Follows nDataAvail
SELECT Xflag In Extensibility flag. Not used in Byte mode.
nERROR nDataAvail In Set low by peripheral to indicate that reverse data is available.
DATA[8:] DATA[8:1] Bi-Di Used to provide data from peripheral to host.

Tab. 8. Byte Mode Signals

EPP Mode

EPP - Enhanced Parallel Port protocol was originally developed by companies Intel, Xircom and Zenith Data Systems to provide powefull connection through parallel port and still was compatible with standard LPT. This protocol was for the first time implemented in 386SL chipset (82360 I/O chip). After this it became a part of the IEEE 1284 standard.

The effect of this mode is data rate between 500kbps and 2Mbps. The transfer is as fast as data rate of the slowest communicating devices. The rate is found from changings of messages and responses from handshake signals nWait and nDataStrobe ( figure 7.).

EPP protocol provides 4 transfer cycles:

  1. Data Write Cycle
  2. Data Read Cycle
  3. Adress Write Cycle
  4. Adress Read Cycle

Data cycles are intended for data transfer between PC and peripherials. Address cycles are intended for channel address tranfer or command and control information. Both are neccessery to show as two different transfer cycles.

SPP Signal

EPP Signal Name

In/Out

EPP Signal Description
nSTROBE nWRITE Out Active low. Indicates a write operation High for a read cycle.
nAUTOFEED nDATASTB Out Active low. Indicates a Data_Read or Data_Write operation is in process.
nSELECTIN nADDRSTB Out Active low. Indicates an Address_Read or Address_Write operation is in process.
nINIT nRESET Out Active low. Peripheral reset.
nACK nINTR In Peripheral interrupt. Used to generate an interrupt to the host.
BUSY nWAIT In Handshake signal. When low it indicates that is OK to start a cycle (assert a strobe), when high it indicates that it is OK to end the cycle (de-assert a strobe).
D[8:1] AD[8:1] Bi-Di Bi-directional address/data lines.
PE user defined In Can be used differently by each peripheral
SELECT user defined In Can be used differently by each peripheral.
nERROR user defined In Can be used differently by each peripheral.

Tab. 9. EPP mode signals Definitions

Figure 5. shows one of the data write cycle. CPU signal nIOW emphasizes all handshake which come on one I/O cycles.


Fig. 7. EPP Data Write Cycle

Data Write cycle phase transitions:

  1. Program executes an I/O write cycle to port 4 (EPP Data Port)
  2. The nWrite line is asserted and the data is output to the parallel port
  3. The data strobe is asserted, since nWAIT is asserted low
  4. The port waits for the acknowledge from the peripheral (nWAIT deasserted - high)
  5. nDataStrobe is deasserted and the EPP cycle ends
  6. The ISA I/O cycle ends
  7. nWAIT is asserted low to indicate that the next cycle may begin

 

Fig. 8. EPP Address Read Cycle

Note : The parallel ports with EPP before standardization IEEE 1284 can have little bit different process of some handshake signals.

EPP Register Interface

The following table 10. describes extended registers in comparison with SPP mode. As was written higher, SPP mode uses 3 basic registers: Data, Status and Control Register. EPP mode extents them about several new registers as it is in the table 10, which presents register offsets from base port address.

Port Name Offset Mode Read/Write Description
SPP Data Port +0 SPP/EPP W Standard SPP data port. No autostrobing.
SPP Status Port +1 SPP/EPP R Reads the input status lines on the interface.
SPP Control Port +2 SPP/EPP W Sets the state of the output control lines.
EPP Address Port +3 EPP R/W Generates an interlocked address read or write cycle.
EPP Data Port +4 EPP R/W Generates an interlocked data read or write cycle.
Not Defined +5 to +7 EPP N/A Used differently by various implementations. May be used for 16 and 32 bit I/O.

Tab. 10. EPP Register Definitions

An easy attempt for writing on base address + 4 can find, if the device supports this communation mode.

ECP Mode

The Extended Capability Port, or ECP, protocol was proposed by Hewlett Packard and Microsoft as an advanced mode for communication with printer and scanner type peripherals. Data rate in this mode can be up to 800KBps without using DMA ( Direct Memory Access) and up to 2MBps with help of DMA. It's true in implementation on ISA bus. Nowadays LPT interface implemented on PCI bus can reach up to 3 or 5 MBps. Sometimes it's presented possibility up to 8MBps.

 The ECP protocol provides the following cycle types in both the forward and reverse directions:

  1. Data cycles
  2. Command cycles

Full register implementation and description can be found in Microsoft document: "The IEEE 1284 Extended Capabilities Port Protocol and ISA Interface Standard" (ecp_reg.pdf). This document defines features and implementation which IEEE 1284 standard doesn't appreciate. As example Run_Length_Encoding (RLE) data compression, FIFO buffers, DMA and programming too.

RLE enables real-time data compression with ratio up to 64:1, but it have to be permited on both communicating devices.

Plná registrová implementace a popis lze nalézt v dokumentu Microsoft: "The IEEE 1284 Extended Capabilities Port Protocol and ISA Interface Standard" (ecp_reg.pdf). Tento dokument definuje vlastnosti a implementaci, které IEEE 1284 standard nepostihuje. Jako například Run_Length_Encoding (RLE) datovou kompresi, FIFO buffery, DMA i programování.  It's advantageous for example in transfer of large data amount of a picture from a scaner. Channel addressing is different from EPP mode. The ECP addressing (Channel addressing) is intended for addressing of many logical devices by one physical device. For example to one parallel port are connected FAX, printer and modem. Using ECP channel addressing it's possible accesses to each one. So it's possible to receive data from the modem during the time when data channel is busy because of printer printing.

In basic communication mode during busy signal from printer isn't able to communicate with others devices. In ECP mode is enough only to address other logical channel and communication can proceed. In the same way as other extended modes ECP protocol redefines classical SPP signals and adds other signals for ECP handshake.

 

SPP Signal ECP Mode Name In/Out Description -- Signal usage when in ECP Mode data transfer
nSTROBE HostClk Out Used with PeriphAck to transfer data or address information in the forward direction.
nAUTOFEED HostAck Out Provides Command/Data status in the forward direction. Used with PeriphClk to transfer data in the reverse direction.
nSELECTIN 1284Active Out Set high when host is in a 1284 transfer mode.
nINIT nReverseRequest Out Driven low to put the channel in reverse direction.
nACK PeriphClk In Used with HostAck to transfer data in the reverse direction.
BUSY PeriphAck In Used with HostClk to transfer data or address information in the forward direction. Provides Command/Data status in the reverse direction.
PE nAckReverse In Driven low to acknowledge nReverseRequest.
SELECT Xflag In Extensibility flag.
nERROR nPeriphRequest In Set low by peripheral to indicate that reverse data is available.
Data[8:1] Data[8:1] Bi-Di Used to provide data between the peripheral and host.

Tab. 11. ECP Mode Signals

Figure 9 shows two forward data transfer cycles. When HostAck is high it indicates that a data cycle is taking place. When HostAck is asserted low, a command cycle is taking place and the data represents either an RLE count or a Channel address. Bit 8, of the data byte is used to indicate RLE vs. Channel address. If bit 8 is 0, then bits 1-7 represent a Run_Length Count (0-127). If bit 8 is 1, then bits 1-7 represent a Channel address (0-127).

 

Fig. 9. ECP Forward Data and Command Cycle

Note: Because in ECP mode FIFO buffers are used, it's necessary to point out that receiving device has valid data in FIFO buffer in time point 4, thus after pass of signal HostClk in high level. Between points 3 and 4 it's possible to interrupt trasfer. Then it isn't guaranteed that data was successfully transfered.  

Figure 10 shows a reverse channel command cycle followed by a reverse channel data cycle. The I/O read or write strobes are not shown in these figures. This is because the ECP FIFOs are used to decouple the ISA data transfers, either DMA or programmed I/O, from the actual host/peripheral data transfers. It is this decoupling of the transfer states that makes the ECP protocol a "loosely coupled" protocol. The software driver does not know the exact state of the data transfers. If a large block is being transferred via DMA, the driver does not know if the 123rd byte is being transferred or the 342,201st byte. As in the case of printers, the software may not care. The only concern is whether the transfer was completed or not. Therewithal this picture shows differents between ECP mode ans EPP mode. In EPP mode software can mixes mode of reading and writing on line. On the contrary in ECP mode device have to inquire of reverse data transfer with help of signals nReverseRequest a nAckReverse. Then have to wait for finishing DMA transfer or interrupt from DMA.

 

Fig. 10. ECP Reverse Data and Command Cycle

ECP Software and Register Interface

The Microsoft specification, "The IEEE 1284 Extended Capabilities Port Protocol and ISA Interface Standard", defines a common register interface for ISA based 1284 adapters with ECP. This specification also defines a number of operational modes that the adapter can operate under. Table 12 identifies these modes.

Mode Description
000
 SPP mode
001
 Bi-directional mode (Byte mode)
010
 Fast Centronics
011
 ECP Parallel Port mode
100
 EPP Parallel Port mode
101
 (reserved)
110
 Test mode
111
 Configuration mode
Tab. 12. ECR Register Modes (they set in ECR register - previous Tab. 13.)

Note: The EPP mode isn't specified by ECP protocol, but it's implemented in most controllers.

The ECP Register model comes out from standard parallel port, but it defunes 6 registers which describes the following table 13. Important register definition depends on just settings of the ECP mode ( previous table 12.).

Offset Name Read/Write ECP Mode Function
000 Data R/W 000-001 Data Register
000 ecpAfifo R/W 011 ECP Address FIFO
001 dsr R/W all Status Register
002 dcr R/W all Control Register
400 cFifo R/W 010 Parallel Port Data FIFO
400 ecpDfifo R/W 011 ECP Data FIFO
400 tfifo R/W 110 Test FIFO
400 cnfgA R 111 Configuration Register A
401 cnfgB R/W 111 Configuration Register B
402 ecr R/W all Extended Control Register

Tab. 13. ECP Register Description

From reason of the topic comprehension, I won't describe particular bit definition in each from 6 registers. An interested person can find it in a very detailed description of Microsoft specification: "The Extended Capabilities Port Protocol and ISA Interface Standard", which is a part of document ecp_reg.pdf, or a datasheet of a particular I/O controller.

LPT Program Access

For programming
DOS / Windows 95, 98, Me Windows NT4, 2000, XP

For program access under operating system MS-DOS, it's possible to use only direct commands of programming language for direct access to LPT registers.

Commands summary for direct access in Pascal, C, assembler x86 and Basic language are released in the following text file

For program access under OS Windows 95/98/Me it's possible to find a lot of universal drivers for common users and programmers for direct access under Windows 95/98. For example:

  • port.dll - port.zip - very good driver for access in Windows 95/98/Me. Driver is also part of CD-ROM in the czech book: Burkhard Kainka, Hans-Joachim Berndt : Využití rozhraní PC pod Windows, it's shopped by BEN. The book contains a lot of practical source programs for Visual Basic and Delphi.

 

With coming of OS Windows based on NT core, it appears problems with parallel port access. Programs written with classical direct access to LPT, which works under OS DOS and Windows95/98, will not work properly. This programs can't be used, because they show an error message like "The exception privileged instruction occurred in the application at location ...." and they are interrupted. It's caused by Windows NT/2000/XP security for being more stable system. Windows NT assigns some privileges and restrictions to different types of programs running on it. It classifies all the programs in to two categories , User mode and Kernel mode, running in ring3 and ring0 modes. Generally written programs running in User mode aren't allowed to access to LPT port using certain instructions like IN, OUT etc.. Whenever the operating system find that a user mode program is trying to execute such instructions, the operating system stops execution of those programs and will display an error message .In Kernel mode isn't such restrictions so it is neccessary to use a driver which runs there. Then the driver can be used for LPT port access by the program which access needs.

Because writing a such driver isn't an easy job, at the internet is possible to find a lot of univesal drivers for users and programmers requirements. They usually allows to write and read data from LPT sometimes some other features. For example:

I tested each driver for writing and reading to LPT port with address 0x378 in programming language C++ (program C++ Builder 5).

Here is source program which can be used as an example of using dll drivers in C++ programs.
For older programs under Windows NT4/2000/XP
Generally Some programs

As it was mentioned higher, every program uses access to PC parallel port, which was programmed for OS DOS and Windows 95/98, can't work alone and independent on OS Windows. Under Windows NT/2000/XP should be used some universal program which runs on background of Windows and enables running older programs with direct access to LPT port.
  • UserPort - userport.zip - program for access to LPT port under Windows 2000/XP for older otherwise functionless programs (pack also contains source program with drivers for Windows) .
  • PortTalk - porttalk22.zip - program for access to LPT port under Windows 2000/XP for older otherwise functionless programs. Pack also contains source program with drivers for Windows including an example of access in C language.

Note: Both programs was tested as functional under Windows XP

LPT Control Programs

DOS / Windows 95, 98, Me Windows NT4, 2000, XP
  • Ka - ka.zip - program for reading and setting pins of parallel port + next operations (generator TTL etc.), program works under Windows XP, too.
Program Ka
  • DLPortIO - port95nt.exe - program for data (Byte or Word) reading and writing to selected LPT port (pack contains drivers for Windows).

Note : Here presented programs was tested as fully functional under OS Windows 98 or XP (Programy zde uvedené byly odzkoušeny jako plně funkční v OS Windows 98 nebo XP (according to program).

IO for LPT/ IEEE 1248

Generally

LPT (IEEE 1284) port and communication offer very easy using, because communication uses classical TTL signals. That enables making low cost interface for every device communicates with PC. It's only neccessary to use a I/O buffer for PC LPT port protection, some 8-bit buffer / driver (for example 74LS244, 74LS367 / UL2803 or 8-bit shifter ( 74HC165).

If you want to use all advantages and IEEE 1284 protocol modes, it necessery to take a special integrated circuit like circuits in the next list.
IEEE 1284 Integrated Circuits datasheets

DOWNLOAD & Links

Programs and drivers
Documentation
  • Detailed LPT pins description (1page) - pppinout.pdf
  • Detailed parallel port description and its modes (17 pages) - parallel.pdf
  • Very detailed LPT ECP mode description with registers description. (53 pages) - ecp_reg.pdf
Datasheets

 

LPT Literature in Czech

  • Götz Sören, Mende Reiner : Měření, řízení a regulace s Delphi, BEN 2004 - LPT port and EPP mode description with examples
  • Matoušek David : Udělejte si z PC... 1. díl , BEN 2004 - program access to LPT port under Windows and DOS
  • Matoušek David : Udělejte si z PC v Delphi..., 1.díl, BEN 2003 - program access to LPT port in SPP mode
  • Matoušek David : Udělejte si z PC... 2. díl , BEN 2004 - LPT port in standard SPP/EPP/ECP
  • Burkhard Kainka, Hans-Joachim Berndt : Využití rozhraní PC pod Windows, HEL 2000 - using LPT port under Windows 95/98
  • Vlach Jaroslav : Počítačová rozhraní, BEN 2000 - LPT port general description

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