Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!samsung!interlan.InterLan.COM!interlan.interlan.com!yetsko From: yetsko@interlan.interlan.com (Mike Yetsko) Newsgroups: comp.sys.tandy Subject: Re: File transfer software for TRS-80 model 100? Message-ID: Date: 19 Dec 90 13:34:46 GMT References: <1990Dec12.123645.16070@ugle.unit.no> <1990Dec16.065138.28200@techbook.com> Reply-To: yetsko@interlan.interlan.com Organization: Racal InterLan, Inc., Boxborough, MA (1-800-LAN-TALK) Lines: 24 In-reply-to: fzsitvay@techbook.com's message of 16 Dec 90 06:51:38 GMT In article <1990Dec16.065138.28200@techbook.com> fzsitvay@techbook.com (Frank Zsitvay) writes: > ever heard of the MAX232 chip?? Well, the 100 was introduced long before I ever heard of the MAX232. Since then I HAVE heard of the MAX232, and the MAX233, and I've used them in designs. While it is no big deal to hang a 555, or even use the processor(oh my god!) to generate +/- 12, but my recollection is the 100 was +/-5v, not +/- 12. This should make no difference, as the spec specifically states the port only has to maintain +/-3volts into the receiver under load. No big deal, right? The problem is various vendors of OTHER equipment put series limiting resistors, and this prevented the 100 fro working correctly. The 100 wouldn't work reliably with the Tandy DC-1200 modem for EXACTLY this reason, and all it took was changing (or shorting) the resistors in the DC-1200. That problem could just as likely been present with a +/- 12 volt output level, if it was current limited to too low a value. I will go back and check my 100 when I get a chance and see what it is, but it is low priority to do so. Mike Yetsko