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

Robert Darlington rdarlington at gmail.com
Sun May 23 01:47:10 UTC 2010


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
>>
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>




More information about the Time-nuts_lists.febo.com mailing list