[time-nuts] Z3805 utility, Was: AW: (no subject)

WB6BNQ wb6bnq at cox.net
Sun May 23 04:26:19 UTC 2010


Bob,

For the sake of propriety please don't propagate myths.  The RS- series of standards predate Radio Shack.  The wiki at the following address has a good write-up about it:

http://en.wikipedia.org/wiki/RS-232

And, yes it is standardized.  Although many have abused it.

Bill....WB6BNQ


Bob Camp wrote:

> Hi
>
> In this case the RS relates to Radio Shack ......
>
> Not a lot of standardization in the RS-232 world. Take a look at the slew rate limiting requirements in the original document ...
>
> Bob
>
> On May 22, 2010, at 9:47 PM, Robert Darlington wrote:
>
> > Was there ever a standard?  I always thought the "RS" stood for
> > Recommended Standard, as in "you *should* do the following" as
> > compared to "you shall do the following"  I've seen inverted TTL talk
> > to the RS232 port on laptops and I even sometimes use the max233's
> > (+/- 10 volts instead of 12), but always use the full max232 with
> > external charge pumps when it's a gadget that needs to work everytime
> > with systems from multiple countries.
> >
> > -Bob
> >
> > On Sat, May 22, 2010 at 7:21 PM, Didier Juges <didier at cox.net> 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.
> >>
> >> Didier
> >>
> >> ------------------------ Sent from my BlackBerry Wireless thingy while I do other things...
> >>
> >> -----Original Message-----
> >> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> >> Date: Sun, 23 May 2010 10:39:21
> >> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
> >> 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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
> >>>
> >>>
> >>>
> >>>
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> >>
> >>
> >>
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