On 23 May 2010 13:21, Didier Juges <[email protected]> wrote: > Bruce, > > Thanks for the additional information. > > +/- 14V is quite unusually low in my experience. I typically use Maxim parts > such as the MAX220 series, which is specified at +/-25V for no damage on the > inputs (some parts in that series go to +/-30V). > > The bottom line is that as I pointed out earlier, there is no such thing as > an RS-232 standard any more.
I don't ever think there ever was a RS-232 "standard" implementation as the standards documentation was woolly in parts and left manufacturers to interpret it their own way. I my experience the only way of guaranteeing compatibility was to buy both ends from the same supplier. The spec comes from a time when there was a separate calling unit (the dialling part) and a modem part (just the mod and demod parts). It works fine when talking between a DTE and a true DCE but breaks down when you try to mix them especially if one or both of them expects hardware handshaking as to the standards spec. I used to work in telecoms and this frequently became a nightmare back then as most equipment demanded a full hardware handshake. I have RS-232 burned on my brain like fear and loathing :) Steve > Didier > > ------------------------ Sent from my BlackBerry Wireless thingy while I do > other things... > > -----Original Message----- > From: Bruce Griffiths <[email protected]> > Date: Sun, 23 May 2010 10:39:21 > To: Discussion of precise time and frequency measurement<[email protected]> > Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject) > > Didier Juges wrote: >> Bill, I think you got it backwards. +/- 12V is typical for RS-232, 0/+5V is >> for RS-422 and RS-485. >> >> No RS-232 receiver should be damaged with +/- 12V or even +/- 15V because >> that is their normal operating voltage. >> >> Also, RS-422 and RS-485 have something like 25V common mode tolerance (not >> sure what the actual spec is there,) so that the RS-422 and RS-485 receivers >> should not be damaged by 15V either. The RS-422 drivers are pretty low >> impedance, while the RS-232 drivers are current limited, so I don't think >> that connecting an RS-232 driver into an RS-422 driver will damage either. >> > Picking one RS485 receiver (ADM1485) at random the receiver absolute > maximum (no damage) input range is -14V to +14V. > The RS485 receiver operating common mode range is -7V to +12V. > RS422 receivers have an input operating range of -7V to +7V. > The no damage RS422 receiver input ratings may be higher. >> However, most recent (<10 years?) RS-232 receivers will work with a 0/+3V or >> 0/+5V input, conveniently having a threshold a few 10's or 100's of mV above >> ground, even though the original RS-232 spec required receivers that work >> with as low as +/- 3V, and drivers that deliver +/- 9V minimum. Many >> commercial systems use +/- 5V drivers for RS-232 (B&B Electronics sells a >> lot of converters with these voltages). This is a deliciously sloppy spec >> that nobody has met in the last 25 years probably, yet works most of the >> time. >> >> The one thing to avoid is to short an RS-422 (or RS-485) driver to ground, >> as that can actually cause damage, maybe not every time, but definitely not >> recommended. These have relatively high current output capability to drive >> long lines. >> >> Didier KO4BB >> >> >> > Bruce >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Bill Hawkins >> Sent: Saturday, May 22, 2010 3:09 PM >> To: 'Discussion of precise time and frequency measurement' >> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject) >> >> When all else fails, get out the voltmeter. >> >> Do you have power to the antenna? Is it the right voltage? All the way to >> the antenna? >> >> What volts are on pins 2 or 3 relative to pin 7 in the comm connector? >> >> If you see 12 volts, that's RS-422. You may have burned out your computer's >> serial port. >> >> If you see less than 5 volts, that's RS-232 and all should be well, unless >> you see zero volts. >> >> I may have the RS-xxx volts somewhat off because my memory isn't what it >> used to be. >> >> The guy you bought it from should be able to help with comm basics. >> >> Bill Hawkins >> >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Robert Benward >> Sent: Saturday, May 22, 2010 2:08 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] Z3805 utility, Was: AW: (no subject) >> >> Hi All, >> I hooked everything up and I still get nothing. I can't seem to establish >> communications with the Z3805. I tried a >> null modem as well, in case the cable (supplied) was wired with the wrong >> connector gender. I see a green blinking >> light inside, it he left rear corner of the box. Everything is warm, but >> nothing else. Any ideas? >> >> Bob >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Steve Rooke - ZL3TUV & G8KVD A man with one clock knows what time it is; A man with two clocks is never quite sure. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
