Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!lll-lcc!ames!ucbcad!ucbvax!noah.arc.CDN!kenw From: kenw@noah.arc.CDN.UUCP Newsgroups: comp.os.cpm Subject: A problem with my parallel output port (HELP, please) Message-ID: Date: Fri, 8-May-87 00:05:03 EDT Article-I.D.: SIMTEL20.KPETERSEN.12300627259.BABYL Posted: Fri May 8 00:05:03 1987 Date-Received: Sat, 9-May-87 07:44:01 EDT Sender: daemon@ucbvax.BERKELEY.EDU Distribution: world Organization: The ARPA Internet Lines: 20 Patching the stuff in is (should be) trivial. It's a matter of reassembling your BIOS with the appropriate device handler stuff included. Since you appear to know 8080 assembler and how to handle a parallel port, the rest should be easy. I ASSUME you have the BIOS source. Without it you're stuck. At the very beginnning of BIOS are a bunch of CALL instructions. These are the standard BIOS entry points for all the things the BIOS does. I don't have my books here, so I can't tell you exactly which one it is. Your listing should have it commented/labeled as LSTOUT or some such. The character to be printed will be expected in a register, probably C. Your LSTOUT routine should wait until the printer's not busy, send the character, and return. I don't think return status is important here. As I said, you really need your BIOS listing. Read the existing code to see what it does, following the path from the entry point at the top. It also helps to have access to a CP/M Internals book. One of the best (I can't remember the title) was written by Donald Cortesi of Dr. Dobb's Journal. All you really need are the BIOS entry point and register-handling conventions. You MIGHT want to worry about the USTAT byte for device redirection (via STAT), but I never bother with that. Good luck. /kenw