8-bits as terminals (Was: Serial Multiplexor)

On Mon, 14 Jun 1999, Arfon Gryffydd wrote: I don't know about $25, but I do know of one that sells for around $299 that is 8-ports, uses 1 IRQ (from 3-15) and is a pretty damn nice board to work with. It been tested in several OS's, including DOS, WIN95, WINNT, and several flavors of Unix, and just maybe Linux (though I'm not sure). You can chain up to 4 of these cards together for a total of 32 ports on one interrupt. The board can be configured for base addresses from 200h through 360h. The board has a 16550 for each port. To a communications program, it looks just like a normal serial port so its easy to hack and write drivers for. For instance, I can get it to work with ProcommPlus with little effort. It helps that ProcommPlus is such a fine program, but it has a setup whereby you can assign the base address and interrupt for each COM port. Each port on the board is the base address + (8 * (p - 1)) where p = the port number. So if the board is jumpered at 280h, you'd have port 1 at 280, port 2 at 288, port 3 at 290, 298, 2a0, 2a8... The interrupt is the same for each port. So I just program the base addresses for each COM port in ProcommPlus (up to 8) and the same interrupt and I can now access every serial port on the card. Nifty! $299 is still pretty steep for a fun-project, but I can't think of anything else, besides getting lucky and finding one at a swap meet or whatnot. I once scored a 16-port Digiboard and external connector box for like $5 at a local computer recycler. Almost new, in the box. I'm planning to either use it or the above mentioned multi-port card for when I finally get my classic computer host online. You can find the multi-port card for sale at the following web site. I don't think these guys are the only distributor, and in fact you should shop around because this web site is a software house that develops the C serial port communications library I use in my projects, and so I'm sure they are charging a premium. http://www.wcscnet.com/Hardware.htm The 4th card in the list is what I use. It comes with an external pod that has the actual DB-25 connectors on it and connects to the card via a big fat cable. Careful with this one if by chance you end up ordering one...I've had two bad cables from the factory from the 15 or so that I've ordered. Some of the lines were broken inside the cable, so that some lines were missing on some ports. It doesn't affect all the ports, and it doesn't the ports in the same way if more than one line is broken. There's also a 4-port card listed there, and there are cards that do RS-422. The card is manufactured by Decision Computer Group. What do you know? Here's their website: http://www.decision.com.tw/ Sellam Alternate e-mail: dastar(a)siconic.com ------------------------------------------------------------------------------ Don't rub the lamp if you don't want the genie to come out. Coming this October 2-3: Vintage Computer Festival 3.0! See http://www.vintage.org/vcf for details! [Last web site update: 05/25/99]