4 PC printer ports

"Randy Day" schreef in bericht news:ubv1h.230457$R63.31804@pd7urf1no...

Never seen. But the schematic of the original parallel port should be someware. To make more ports, you'd only change the address decoder logic. Unfortunately I have only one copy of 'a' parallel printerport schematic that's so badly readable you need an old TTL databook and a good description of the ISA card connector and one of the centronics connector and at least some experience to recover the original text. So the pinnumbers, -names and IC types. It uses some ten old LS-TTL chips. If you want it, I can make a scan but you're warned.

petrus bitbyter

If my memory serves me right the original PC spec only allowed for 3 printer ports at the hardware / BIOS level.

Graham

Eeyore wrote in news: snipped-for-privacy@hotmail.com:

You could have more, I'm sure, but good luck with software. If they're not at one of those locations (and the 0278H is questionable at best) you're probably not going to get to use them all.

Puckdropper

You could do it with a multiport card

or similar. Or USB to parallel.

I remember isa cards with one port only. You had to put a strap on to select 1/2/3/4, and the lpt bios area supports 4 printerports. So if you have the extra slots, and can find the cards........

Not that I know of, but read on...

If you want them in order to run a bunch of printers, the easy answer is to use networked or USB printers, of which you can attach as many as you like. If you need to run existing, parallel-only printers, you can buy USB to parallel converters. If you want the ports for general I/O purposes (eg; machine control), you can buy kit or pre-built USB parallel I/O modules very easily, & they're usually also available with extras like analog I/O ports & high level language libraries. '

You can also add more to the official experimental I/O addressing range that starts from 0x300, with the same caveats about software support:

If you don't mind configuring them manually, it's actually not difficult.

Could be. I never saw more than 3 parallel ports on a PC.

They're all over eBay (720 items found for usb parallel) or try any Staples etc.

Somehow I got it in my head it was 4, but you could be right. That would explain why I saw some 3 port cards, but no 4's.

Oh, well, a slight readjustment of plans is in order...

You might be able to 'frig it' but it'll need some code I expect. Like a Bios extension.

Graham

If the latter case, the other thing you can do is make a little multiplexer. There are lots of ways this can be done, but the simplest is to use 2 bits from the CTRL port to select one of 4 addresses that you decode to 4 separate lines, one for each of 4 octal latch enables. The latches are all connected in parallel to the DATA port. Now when you write data, it only goes to the selected latch pins. You can easily extend this scheme at will.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

Only the first BIOSes accounted for four printer ports. Newer ones use the space of the fourth port for controlling some memory extension. FAIK even most or all XT machines could have only three printer ports (as far as the BIOS concernes.)

petrus bitbyter

From Ralf Browns (int53) listings:

----------M00400006-------------------------- MEM 0040h:0006h - BASE I/O ADDRESS OF FOURTH SERIAL I/O PORT Size: WORD Note: the BIOS sets this word to zero if is unable to find more than three serial ports at the addresses it is programmed to check at boot SeeAlso: MEM 0040h:0000h,MEM 0040h:0002h,MEM 0040h:0004h,MEM 0040h:0008h SeeAlso: MEM 0040h:007Fh

----------M00400008-------------------------- MEM 0040h:0008h - BASE I/O ADDRESS OF FIRST PARALLEL I/O PORT Size: WORD Notes: the BIOS POST routine fills in the parallel port address fields in turn as it finds parallel ports. All fields beyond the last one for which a valid parallel port was found are set to zero. the BIOS INT 17 handler uses these fields to address the parallel ports SeeAlso: MEM 0040h:0000h,MEM 0040h:000Ah,MEM 0040h:000Ch

----------M0040000A-------------------------- MEM 0040h:000Ah - BASE I/O ADDRESS OF SECOND PARALLEL I/O PORT Size: WORD Note: zero if fewer than two parallel ports installed SeeAlso: MEM 0040h:0002h,MEM 0040h:0008h,MEM 0040h:000Ch

----------M0040000C-------------------------- MEM 0040h:000Ch - BASE I/O ADDRESS OF THIRD PARALLEL I/O PORT Size: WORD Note: zero if fewer than three parallel ports installed SeeAlso: MEM 0040h:0004h,MEM 0040h:0008h,MEM 0040h:000Ah,MEM 0040h:000Eh

----------M0040000E-------------------------- MEM 0040h:000Eh - BASE I/O ADDRESS OF FOURTH PARALLEL I/O PORT (pre-PS/2) Size: WORD Note: zero if fewer than four parallel ports installed SeeAlso: MEM 0040h:0008h,MEM 0040h:000Ah,MEM 0040h:000Eh"BIOS DATA"

----------M0040000E-------------------------- MEM 0040h:000Eh - SEGMENT OF EXTENDED BIOS DATA SEGMENT (PS/2, newer BIOSes) Size: WORD SeeAlso: MEM 0040h:000Eh"PARALLEL"

Funny you should mention that ! I came across an old 8 bit ISA LPT card earlier today with an 8 pin dil header that you soldered wires across to select the port. I remember that you could turn the header plug around to select 1 or 3 and a second one to get 2 or 4 !

I always used to wonder why jumpers and pins weren't used.

Because a header plug in a socket is cheaper.

Cheers! Rich

Mmm. I would have thought the reverse ! Probably today it would be! 20 years ago ???

More important, if the board was to be used on a production line it takes less time to change the configuration, and harder to screw up.

But what will you do for interrupts?