Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!necntc!necis!encore!paradis From: paradis@encore.UUCP (Jim Paradis) Newsgroups: comp.os.minix Subject: Problems with serial TTY driver Message-ID: <2314@encore.UUCP> Date: Tue, 8-Dec-87 11:57:28 EST Article-I.D.: encore.2314 Posted: Tue Dec 8 11:57:28 1987 Date-Received: Sun, 13-Dec-87 11:45:19 EST Organization: The Whizzo Chocolate Company Lines: 31 After many weeks of not quite being able to get around to it, I finally added serial line support to my rewritten MINIX TTY driver. It works, but there's one serious problem: If I test it out by looping back transmit and receive on the serial line and running a quick&dirty terminal program, if I type at it too fast the system will hang. Now, I remember someone else in this newsgroup sometime back who added serial capabilities to the stock TTY driver and ended up with the same problem. Is there some limit to how fast MINIX will take interrupts? If one takes them too fast, will messages get lost? A little background info: I'm running a 12 MHz AT-clone with an AST-sixpack-clone board for serial I/O. The TTY driver takes interrupts for both "data ready" and "transmit register empty". I've tried a number of techniques for minimizing the number of interrupts processed, including doing all writes synchronously (thereby only having to process data-ready interrupts), waiting around for a period of time after a character comes in to see if there's another immediately following, all to no avail. I'm running the serial line at 1200 baud (the default MINIX ioctl structure has no way of specifying baud rates, so it's hard-coded for now. Eventually I'll fix ioctl). Any ideas out there? Am I missing something obvious? +----------------+ Jim Paradis linus--+ +--+-------------+ | Encore Computer Corp. necntc--| | | E N C O R E | | 257 Cedar Hill St. ihnp4--+-encore!paradis | +-------------+--+ Marlboro MA 01752 decvax--| +----------------+ (617) 460-0500 talcott--+ But if we took the bones out it wouldn't be crunchy, now would it?