AW: AW: [En-Nut-Discussion] Second RS232 port

[Ernst Stippl]

Hi!
The DS275 generates its power from theincoming data signal - provided - the
signal ist there and strong enough.

The MAX232 needs an external 5V supply and generates the +/-12V RS232
signals thru internal circutry plus 4 external capacitors.   

That is quite a difference, I think.

Look at: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2929 This first
paragraph reads:

The DS275 Line-Powered RS-232 Transceiver Chip derives power from the data
line providing an extremely low-cost and low-power RS-232 serial port
interface. The receiver input translates RS-232 signal levels to common
CMOS/TTL levels. The transmitter circuit steals current from the receive
RS-232 signal when that signal is in a negative state (marking). Since most
serial communication ports remain in a negative state statically, using the
receive signal for negative power greatly reduces the DS275's static power
consumption



regards

 
ernst


-----Ursprüngliche Nachricht-----
Von: en-nut-discussion-bounces at egnite.de
[mailto:en-nut-discussion-bounces at egnite.de] Im Auftrag von Elan Feingold
Gesendet: Mittwoch, 23. August 2006 09:37
An: Ethernut User Chat (English)
Betreff: Re: AW: [En-Nut-Discussion] Second RS232 port

I was planning to hook it up to a standard PC's serial port; should this be
a problem? What about the DS275 is different than the MAX232, I had a look
at the data sheet and nothing jumped out.

Many thanks,

-elan

> Yes, a MAX232 sounds reasonable, the DS275 should (in my opinion) only
> be used when it is *sure* that the "other side" tolerates the way how
> the DS275 works.
>

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