This is the talk page for discussing improvements to the Parallel port article. This is not a forum for general discussion of the article's subject. |
Article policies
|
Find sources: Google (books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL |
This article is rated C-class on Wikipedia's content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||
|
PUT UP A PICTURE!!! PLEASE!!! —Preceding unsigned comment added by 68.255.69.19 (talk • contribs) 20 Nov 2004
Just that. —Preceding unsigned comment added by 59.92.242.21 (talk • contribs) 13 April 2006
Hi:
Regarding whether this should be merged with Parallel Communications/Transmission
First of all, I clicked on "(discuss)" and ended up here. IF I am at an inappropriate place with this comment, my apologies.
Now, I often send people to Wikipedia to research various portions of Computer Hardware, Software, IT, etc. They need to end up at very specific portions of those subjects (such as Parallel Ports, Centronics, and IEEE-1284). IF this portion is merged with other sections, then I hope that the person's ability to get to exactly the pieces of information that they need, will not be impeded by having the information buried amongst tonnes of other information.
Thanks in advance
Ross Tucker Canberra, Australia —The preceding unsigned comment was added by 150.101.125.246 (talk) 21:15, 9 December 2006 (UTC).
External links were filling up with commercial and advertising sites and were removed. Please add new links that conform to WP guidelines and refrain from adding commercial links WP:EL. - Thanks Calltech 16:52, 18 December 2006 (UTC)
All our information about the parallel port is split into various disconnected sections in at least four different articles, none of which is very useful. They need to be merged into one comprehensive article. --88.110.235.235 22:18, 13 January 2007 (UTC)
The problem here is the various versions of the parallel printer interface:
So: I would recommend this article and an overview of the parallel printer port and linking to the other articles. --Gadget850 ( Ed) 20:54, 15 January 2007 (UTC)
It has been three weeks and only the two of us have discussed this. While looking at this, I see some some basic issues with this article. First is the scope and the name. The scope of the article deals with the printer interface, whereas a parallel port can refer to a great many things. Parallel printer port would be a better title. Currently the article is PC centric- as noted above there were a number of variants and connectors. The article is also Centronics/IEEE-1284 centric as it does not note the Dataproducts paralle interface- a completely different standard. --Gadget850 ( Ed) 15:34, 9 February 2007 (UTC)
This article seems to be about the IBMoid PC implementation of the Centronics-style parallel port, rather than the port itself.
While this information can be useful, and may very well bear inclusion (along with other implementations), the article should discuss the particulars of the interface itself—including signaling, and the 36-pin micro ribbon connector that was originally used at both ends of the cable, before IBM began substituting the DB-25 at the host end.
If there is an unused LPTx slot, the port addresses of the others are moved up. (For example, if a port at 0x3bc does not exist, the port at 0x378 will then become LPT1.) The IRQ lines, however, remain fixed (therefore, 0x378 at LPT1 would use IRQ 7). The port addresses assigned to each LPTx slot can be determined by reading the BIOS Data Area (BDA) at 0000:0408.
Should this in fact read as follows? I'm not sure enough to make the edit.
If there is an unused LPTx slot, the port addresses of the others are moved up. (For example, if a port at 0x378 does not exist, the port at 0x278 will then become LPT1.) The IRQ lines, however, remain fixed (therefore, 0x278 at LPT1 would use IRQ 6). The port addresses assigned to each LPTx slot can be determined by reading the BIOS Data Area (BDA) at 0000:0408.
The current sentence implies that there will be no change, as 0x378 is LPT1 as standard.
The problem is that the table lists the addresses checked in the wrong order. The sequence (according to chapter 14 of The Undocumented PC by Frank Van Gilluwe) is 3BC,378 and finally 278. The 3BC address was used by the parallel port found on the MDA video card while the 378 & 278 were originally found on ISA parallel port cards and later integrated into motherboard chipsets. I will update the table to reflect this. TheGiantHogweed (talk) 11:24, 7 June 2009 (UTC)
A diagram like this would be nice. — Omegatron 22:19, 14 January 2008 (UTC)
The diagram and table seems to contain errors. As they currently stand (July 6, 2015), I believe the following corrections should be considered:
I've made a revised diagram with the above suggested changes here.
For the table mods, I'd suggest if "overline" text can't be entered, use the +/- prefix syntax instead, e.g. -STROBE, -ACK, +BUSY, etc.
Sources for these corrections:
I'd make the changes myself, but I'm not sure I should without some peer review, as the original table + image are heavily referenced. Greg ercolano (talk) 00:36, 7 July 2015 (UTC)
I agree this would be nice to have. AFAIK there is no specification since the port can deliver much faster than a printer, the originally intended peripheral, requires. However the speed is relevant for other uses of the port such as
It may be difficult to find verfiable sources about speed rather than just OR. Cuddlyable3 (talk) 13:32, 24 May 2008 (UTC)
how exactly did the PC variant differ from the original? Plugwash (talk) 03:20, 29 December 2008 (UTC)
What is this pins used for? Are they "reserved"? --MrBurns (talk) 08:51, 6 April 2009 (UTC)
The table is a mess; among other things, it does not list the specification. Per the Centronics Model 101 Interface Specifications (Parallel) and IEEE 1284-1994: Standard Signaling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers:
Pin | Centronics[a] | PC (IBM/Epson)[b] | IEEE-1284[b] |
---|---|---|---|
1 | DATA STROBE | Strobe | nStrobe |
2 | Data 1 | Data 1 | Data 1 |
3 | Data 2 | Data 2 | Data 2 |
4 | Data 3 | Data 3 | Data 3 |
5 | Data 4 | Data 4 | Data 4 |
6 | Data 5 | Data 5 | Data 5 |
7 | Data 6 | Data 6 | Data 6 |
8 | Data 7 | Data 7 | Data 7 |
9 | Data 8 | Data 8 | Data 8 |
10 | ACKNLG | Ack | nAck |
11 | Busy | Busy | Busy |
12 | PE (paper empty) | Paper Empty | PError |
13 | SLCT | Select | Select |
14 | SS (hardware alarm) | AutoFdXT | nAutoFd |
15 | OSCXT (100kHz clock) | not defined | not defined |
16 | 0v | Signal Ground | Logic Ground |
17 | Chassis Gnd | Chassis Ground | Chassis Ground |
18 | 5v | not defined | Peripheral logic high |
19 | Twisted Pair Gnd | Signal Ground (Strobe) | Signal Ground (nStrobe) |
20 | Twisted Pair Gnd | Signal Ground (Data 1) | Signal Ground (Data 1) |
21 | Twisted Pair Gnd | Signal Ground (Data 2) | Signal Ground (Data 2) |
22 | Twisted Pair Gnd | Signal Ground (Data 3) | Signal Ground (Data 3) |
23 | Twisted Pair Gnd | Signal Ground (Data 4) | Signal Ground (Data 4) |
24 | Twisted Pair Gnd | Signal Ground (Data 5) | Signal Ground (Data 5) |
25 | Twisted Pair Gnd | Signal Ground (Data 6) | Signal Ground (Data 6) |
26 | Twisted Pair Gnd | Signal Ground (Data 7) | Signal Ground (Data 7) |
27 | Twisted Pair Gnd | Signal Ground (Data 8) | Signal Ground (Data 8) |
28 | Twisted Pair Gnd | Signal Ground (Ack) | Signal Ground (PError, Select, nAck) |
29 | Twisted Pair Gnd | Signal Ground (Busy) | Signal Ground (Busy, nFault) |
30 | PRIME RET | Signal Ground (Init) | Signal Ground (nAutoFd, nSelectIn, nInit) |
31 | PRIME | Init | nInit |
32 | FAULT | Fault | nFault |
33 | Light Detection (video lamp inop) | Signal Ground (Select In) | not defined |
34 | Line Count | not defined | not defined |
35 | Line Count Return | 5v | not defined |
36 | not defined | Select In | not defined |
IEE-1284 pin 18 is often used to power an external device such as a network print server. Depends on the parallel port and how much current it supplies.
--—— Gadget850 (Ed) talk - 13:58, 6 April 2009 (UTC)
Maybe it is important to note, that modern PC extension cards, like PCI Express parport cards use a logic high level of 3.3V. I've seen pages linking to this Wikipedia-Topic: "but they say its 5V". Just to avoid problems, which I've stumbled. — Preceding unsigned comment added by Jedzia (talk • contribs) 11:43, 30 March 2014 (UTC)
The article contains the following information (apparently added in 2011 by Uwezi ):
Well, this IMHO just does not make any sense why something like this should become the norm. I can, however, see one reason for this to occur, but that is by a design error only and should be regarded as a bug. If someone knows of any legitimate reason for the pin 25 to be left unconnected or knows a particular example of common hardware with this property, please feel free to add a citation and/or further clarification. I have just verified the parallel port wiring on a couple of motherboards and on 1 LPT card (some of which could hopefully be considered modern by the 2011) and found none having the pin 25 not connected to ground. Meanwhile, I'm thus marking this information with ((Dubious))
.
As for the above hinted possible reason for the pin 25 to remain unconnected, I have recently discovered a possibility for this to occur with Gigabyte motherboards. Gigabyte motherboards seem to be using a slightly modified pin-out for the LPT header (pin 24 swapped with key/pin 26) which, if used with a generic-wired (and unkeyed) bracket cable, would leave the pin 25 unconnected. Unfortunately, it seems even Gigabyte themselves are selling brackets with the generic wiring only that are not compatible with their own modified pin-out. I have recently discovered this myself (Czech Republic, as of 2015 – unsuitable bracket bought from one e-shop and the very same being confirmed by another e-shop to be the only available; in both cases the bracket was described along with Gigabyte's part numbers), but this has already been reported as early as in 2009 on Tom's Hardware. However, as noted above, this is a design error in the bracket cable and the pin 25 would be correctly connected to ground with the appropriately wired cable, so this might not have been the reason for putting this information in the article.
And if this was the original reason for putting the information there, the statement should be at least rephrased to reflect the fact this is by a wiring error only. (Which I might do myself some time in the future, if no objections arise...)
--JITR (talk) 15:58, 7 October 2015 (UTC)
My big issue though is why a 25-pin connector had so many pins connected to Ground when these pins could have been put to better use, for example, as additional data lines making the parallel interface capable of 16-bit transfer when it began being used for more than just a printer interface. 81.108.186.222 (talk) 12:55, 6 March 2022 (UTC)
There is a significant gap in the history section between the earliest use of this connector, which per the text here (it's news to me) required the host computer to convert character data into dot matrix bit patterns, and the slightly later usage wherein the 7 data bits in the connector were used to send ASCII characters and the character generation was done in the printer. Certainly the first printers I dealt with that used this interface (on CP/M machines) just took ASCII data. More sophisticated dot-matrix printers did have a "binary" mode that could be used for graphics. Jeh (talk) 14:24, 9 October 2016 (UTC)
It might be worth mentioning that the DataProducts interface was more different than just a different connector. The handshaking was different. I built a couple of interfaces to these back in the 70s. I can probably dig out details on the differences. Jeh (talk) 21:13, 9 October 2016 (UTC)
The table "Bit-to-pin mapping for the Standard Parallel Port (SPP)" uses the tilde (~) to specify inverted signals.
In the good old days of computers, the slash forward was usually used in writing, when the line above was not feasible, e.g. /Strobe, /Busy.
The table designates pins, not signals, but it might nevertheless be more common to use the slash instead of the tilde.
--Stefanhanoi (talk) 18:12, 30 September 2021 (UTC)
What was the idea behind the original IBM hardware assigning an IRQ to the parallel port?
Does a parallel port/printer combination actually generate interrupts, and if so, under what conditions? There's only a few lines like ACK and PAPER OUT that go back into the port in the computer and surely these don't generate an interrupt? Valgrus Thunderaxe (talk) 17:09, 27 June 2022 (UTC)
Is this manufacturer important enough to be included in this page? Their Wikipedia page has no parallel ports mentioned anywhere. 2A01:112F:90C:BD00:5E44:E0F9:CA35:8335 (talk) 14:53, 21 March 2024 (UTC)