Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!unido!horga!veeble!proppi From: proppi@veeble.han.de (Paul Lenz) Newsgroups: comp.os.cpm Subject: Re: Is my machine too SLOW for 2400bps modems? Message-ID: <1991Feb07.160804.20088@veeble.han.de> Date: 7 Feb 91 16:08:04 GMT References: <316@fxrs.intel.com> Reply-To: proppi@veeble.UUCP (Paul Lenz) Organization: veeble Hannover, W-Germany Lines: 38 In article <316@fxrs.intel.com> jmasters@fxrs.intel.com (Justin Masters) writes: > >I have a Radio Shack model 4 w/ Montezuma Micro's CP/M 2.2. >[...] >I'm using Qterm 4.2f and I've also used MEX 1.12 (or some old version like >that). Both worked beautifully for me when I had 1200 baud capability, but >now it seems that 2400 baud is too fast. Is this true? How do I fix it? Is >it a problem of my machine waiting too long at the end of the line before >continuing on to the next line? Yes!!! I had had the same problem. My machine scrolls only when the monitor finishes a picture and the electron ray goes to the upmost line. When my BIOS wants to scroll, it is waiting in an ENDLESS loop for a flag. I found that the vert sync signal makes an interrupt. In the interrupt subroutine this flag is set. The CPU escapes from the endless loop and does the scroll. There are two ways to fix this: 1. I copied the complete scroll routine from the BIOS into the modem program and added a SIO polling routine to the endless loop. In this routine the CPU saves the bytes coming from the modem into a special area. So when the CPU waits for the scroll, it gets every byte from the modem. After the scroll the modem program checks this special area and prints the characters. 2. After that, I finally succeeded to make my Z80 SIO working in interrupt mode. So of course the CPU gets every byte from the modem. Proppi PS: Don't mind my bad english! proppi@veeble.UUCP = Paul Lenz / Friesenstrasse 22 / D-3000 Hannover 1 !unido!horga!veeble!proppi voice: +49 511-342451 / And remember: Rock'n'Roll and CP/M never die!!