EE 316
Computer Engineering Junior Lab
Lecture on PC Parallel port
The IEEE 1284 parallel
interface standard
Parallel ports are used for connecting a computer (host) to
a printer or certain other peripheral devices over a parallel
(eight bits of data at a time) physical and electrical
interface.
Parallel ports conform to the specifications of document of
the Institute of Electrical and Electronic Engineers (IEEE)
called IEEE Std 1284-1994: Standard Signaling Method
for a Bi-directional Parallel Peripheral Interface for
Personal Computers, or IEEE 1284 for short.
http://whatis.techtarget.com/definition/0,,sid9_gci213469,00.html
http://www.lavalink.com/fileadmin/white_papers/ieee1284_parallel_ports.pdf
Modes of operation
(The IEEE 1284 standard)
• Compatibility mode
• Nibble mode
(Default “Forward” mode)
(4-bit “reverse” mode)
• Byte mode
(8-bit “reverse” mode)
• EPP mode
(Enhanced Parallel Port mode)
• ECP mode
(Enhanced Capability Port mode)
Forward: Host to Peripheral
Reverse: Peripheral to Host
Source: http://www.lvr.com/files/ppc1.pdf
25 Pin D-sub or IEEE 1284-A connectors
http://www.lavalink.com/fileadmin/white_papers/ieee1284_parallel_ports.pdf
36 Pin Centronics or IEEE 1284-B connectors
http://www.lavalink.com/fileadmin/white_papers/ieee1284_parallel_ports.pdf
IEEE-1284 compliant
Parallel Printer Cables
Connector Types
IEEE-1284 Printer Type “A” Connector (DB25) This is the connector
most commonly used as the computers parallel port output.
IEEE-1284 Printer Type “B” Connector (CN36) This is the most
commonly used connector for the end of the cable that goes to the
printer.
IEEE-1284 Printer Type “C” Connector (HPCN36) This is a new
connector for the printer end of the cable.
http://www.ramelectronics.net/html/ieee-1284_printer_cables.html
DB-25 Female D-type Connector
(on the computer)
•8 output pins accessed via the DATA Port (bidirectional)
•5 input pins (one inverted) accessed via the STATUS Port (peripheral to HOST)
•4 output pins (three inverted) accessed via the CONTROL Port (output only)
•The remaining 8 pins are grounded
http://www.doc.ic.ac.uk/~ih/doc/par/index.html#index
Addressing
Standard parallel port uses three contiguous addresses:
3BCh, 3BDh, 3BEh (LPT1)
378h, 379h, 37Ah
(LPT1, LPT2)
278h, 279h, 27Ah
(LPT1, LPT2, LPT3))
First Address -- Port base address (data registers)
Second Address -- (base+1) Port’s status registers
Third Address – (base+2) Ports Control Registers
In our lab we have a PCI parallel
card that uses the
Following address:
DF18h, DF19h, DF1Ah
Parallel port output
drive capabilities
The outputs of the data registers are filtered through
A 27 Ohm resistor and a 2.2 nF capacitors.
The numbers can vary substantially between different port types. For fast transitions and
more drive currents it is best to use Schmitt-trigger buffers/inverters at the receiving end.
http://www.hut.fi/Misc/Electronics/circuits/lptpower.html
References
http://www.lvr.com/files/ppc1.pdf
http://whatis.techtarget.com/definition/0,,sid9_gci213469,00.html
http://www.lavalink.com/fileadmin/white_papers/ieee1284_parallel_ports.pdf
http://www.doc.ic.ac.uk/~ih/doc/par/index.html#index
http://www.epanorama.net/circuits/parallel_output.html
http://www.hut.fi/Misc/Electronics/circuits/lptpower.html