laser-lovers@uw-beaver (laser-lovers) (10/26/84)
From: ihnp4!ut-sally!harvard!wjh12!bb@uw-beaver.arpa > From: ihnp4!utzoo!henry@uw-beaver.arpa > We've got an HP LaserJet ($4k laser printer, daisywheel emulation with > minor smarts) on demo right now. It's not bad. .... and one major flame. > > Now, for the bad part. > > The thing wants to talk 9600 baud, 8 data bits, no parity, XON/XOFF. > PERIOD. 9600 baud, ok. No parity, straightforward. But try getting a > V7 (or derivative thereof, like maybe Xenix) to produce an 8-bit data > path with flow control...!?! The LaserJet *must* have a full 8-bit path. > But before you sign a PO, make very > very sure that your Unix can give you a full 8-bit output path without > resorting to raw mode (which deprives you of flow control). HARK! All is not lost! (MAYBE) It is true that the LaserJet wants a `clean' 8-bit data path, and on v7-ish systems, RAW mode is your best bet. However you might be able to get the proper flow control from HARDWARE! In addition to using X-OFF to (temporarily) silence your host, the LaserJet simultaneously drops the DTR (DataTerminalReady) signal on rs-232 pin 20. Now, if your serial line is implemented around any one of a number of reasonable UART's, you can connect the LJ's pin 20 to your host serial pin 5 (sometimes pin 6) which should be CTS. The effect is that when the LJ drops DTR, the low CTS will inhibit transmit-done from being given to your terminal driver; thus output will be suspended, until LJ raises DTR (at same time as sending X-ON), saying it is ready for more goodies. Remember: You can't always get what you want, but if you try some time, you just might find, you get what you NEED. (MJ-KR) Brent Byer (decvax!genrad!wjh12!bb)