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LPT port

Posted on 1998-12-29
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Last Modified: 2012-08-14
It may not be the right place to ask this question, BUT here it is :

I'm in NEED of informations about how does the LPT work, send and recive data

any suggestions or addresses I have to go for ?

Thanks  
anas
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Question by:anas_madani
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by:hddp666
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Try yahoo, hotbot and other search engines using LPT, parallel port, pinout, etc. There are a lot of articles and papers on ports, including how to write programs to control them.
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tracyc earned 20 total points
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I hope your in a reading mood......

The LPT port (parallel port or centronics port), sends many bits of data along eight wires at a time as apposed to the serial port
which sends only one bit of data at a time along one wire.

Comming out of the computer through the 25-Pin parallel connection it works like this:

a) A signal on line 13 (the select line) from the printer or whatever tells the computer it is online and ready

b) Data is sent (at around five volts for a 1 and nearly 0 volts for a 0) on lines 2 through 9.

c) Then line one sends a strobe signal to the device to let that device know it should read the data that was just sent.  (This happens very fast!)

d) Line 11 tells the PC if the device is currently to busy to read the data.

e) Line 10 tells the PC that the device has read the data from lines 2 through 9 and is ready for more.

f) Line 12 tells the PC if the printer is out of paper.

g) Line 15 tells the PC that some error condition exests, but doesn't say what.

h) Line 16 is user to cause the printer to reset itself.

i) Line 14 tells the printer to do advance the paper one line for a carriage return when low-voltage is present or just advance one line for line advance code when high voltage is present.

j) Line 17 is only used on some printers that can use it to receive a code from the PC to turn on or off.

Thats pretty much it.    
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