Re: Hysterical question

[Fred Townsend]

Jaap has already commented on this one but I will follow up as well.  You are indeed looking at the TTL interface side of the MAX232.  It has absolutely nothing to do with RS232 specifications which are pretty unique. The most current spec is the RS232C which hasn't changed in many years.  It defines logic "1" receive levels as minus 3 to minus 25 volts.  A logic "0" is plus 3 to plus 25 volts.  The region between minus 3 and plus 3 volts is specifically defined as "undefined" . In other words, neither a logical "1" or "0".  A copy of the RS232 specification can be purchased from the CCITT in Switzerland. I think it is listed under Modem Interface Standards. One should be very careful in extracting specifications from data sheets.  The parts are not necessarily compliant with the specification.  Many of the Maxim parts are optimized for driving mice rather than modems. Fred Townsend Peter Vogel wrote: No, it's from the data sheet for the MAX232 receiver. The spec for the receiver is quite different from the spec for RS232. On Tue, 16 Dec 2003 00:29:18 -0800 Fred Townsend <[EMAIL PROTECTED]> wrote: These are specs for RS232. Not even close. Do you mean RS422? Fred Townsend Peter Vogel wrote: I'm trying to understand the specifications of an RS-232 receiver. Input threshold low minimum = 0.8V Input threshold high max = 2.4V Hysteresis max = 1V So, am I right in concluding that to operate reliably I need to swing the input over at least -0.2V to 3.4V, or do the threshold specs include the hysteresis? Peter Vogel ZapTV Pty Ltd 30 Adeline St, Faulconbridge 2776 Australia Tel: 02 4751 8735 Fax: 02 4751 2601 email: [EMAIL PROTECTED] -- Author: Fred Townsend INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). Peter Vogel ZapTV Pty Ltd 30 Adeline St, Faulconbridge 2776 Australia Tel: 02 4751 8735 Fax: 02 4751 2601 email: [EMAIL PROTECTED]