stanley@phoenix.com (John Stanley) (11/06/90)
andrew@frip.WV.TEK.COM (Andrew Klossner) writes: > My group makes Postscript printers, which communicate with the host via > RS-232, Appletalk, or a parallel port. When using the first two ports, > you get two-way communication; a Postscript program (executing on the > printer) can write information to the port to be read by the host. > This is not true of the parallel port, which for the printer is > input-only, because the first few generations of PCs could do only > output on their parallel ports. But the parallel port provides the > fastest path to the printer. This means that the user can configure > for two-way printer communication, or for high speed printer output, > but not for both. This is frustrating. The standard I heard a long time ago involved using the parallel port for fast output to the printer, and a serial port for the reverse handshake. I do not remember where I heard this, but I think it was from Adobe as part of the source license for TranScript, or in associated documents. It may have also been in the documentation for the NEC LC-890 series of printers. This sounds like a much cleaner implementation, as you do not need to worry if you have bi-directional parallel hardware, or try to kludge a signal from the printer using the current status line. It does tie up a serial port, but allows standard BIOS calls to handle the I/O. You may find yourself in trouble trying to support all the different hardware variants that exist. Plus, this would allow your new printer to be used on older AT's and XT's. There is a tremendously large market of such beasts. I, myself, am looking for a good PostScript printer to run on an AT. <> "Aneth! That's a charming place!" "You've been to Aneth?" <> "Yes, but not yet." -- The Doctor and Seth, "The Horns of Nimon". >< <> "Sanity check!" "Sorry, we can't accept it, it's from out of state." - me