TTL vs RS-232

About a serial port, is there differences between TTL and RS-232?

QU


0
QuantumUniverses
3/25/2010 3:03:35 PM
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Software - no

-- 
Bruce Eitman (eMVP)
Senior Engineer
Bruce.Eitman AT Eurotech DOT com
My BLOG http://geekswithblogs.net/bruceeitman

Eurotech Inc.
www.Eurotech.com

"QuantumUniverses" <quantumuniverses@gmail.com> wrote in message 
news:uqVErxCzKHA.5288@TK2MSFTNGP05.phx.gbl...
> About a serial port, is there differences between TTL and RS-232?
>
> QU
>
> 


0
Bruce
3/25/2010 3:09:37 PM
> Software - no

Eletrical/hardware?

I know what's RS-232, that a standard which describes the mapping of the
pins used for serial comm.. but what's TTL? Could a RS-232 be a TTL or is it
always?

QU


0
QuantumUniverses
3/25/2010 3:17:56 PM
On 3/25/2010 4:03 PM, QuantumUniverses wrote:
> About a serial port, is there differences between TTL and RS-232?

As Bruce said, there are no difference on the software side.
On the hardware side RS-232 standard requires specific voltage levels (+ 
and - between 5 and 15V IIRC).
TLL usually means that the signals are at the standard voltage of your 
board (in the past 5V,now also 3.3V or 1.8V) even if sometimes it's used 
to mean 5V.
Obviously that means that you can't connect RS232 signals where TTL 
signals are expected and vice-versa (communication will not work and you 
may damage your hardware).
You need a MAX232 or similar chip to convert voltage levels.

-- 
Valter Minute (eMVP)
Training, support and development for Windows CE:
www.fortechembeddedlabs.it
My embedded programming and cooking blog:
www.geekswithblogs.net/WindowsEmbeddedCookbook
Windows Embedded support forums in Italian:
http://social.msdn.microsoft.com/Forums/it-IT/windowsembeddedit/threads
(the reply address of this message is invalid)
0
Valter
3/25/2010 3:25:55 PM
For what it's worth, I have used TTL outputs to drive a regular RS232 port 
and that did work even though out of spec.

You have to be careful to NOT go the other way though; 12V on a 1.8V or 3.3V 
input would be an unpleasant experience.

-- 
Dean Ramsier - eMVP
BSQUARE Corporation


"Valter Minute [eMVP]" <valter.minute@_REMOVEME_gmail.com> wrote in message 
news:%23orU49CzKHA.1064@TK2MSFTNGP04.phx.gbl...
> On 3/25/2010 4:03 PM, QuantumUniverses wrote:
>> About a serial port, is there differences between TTL and RS-232?
>
> As Bruce said, there are no difference on the software side.
> On the hardware side RS-232 standard requires specific voltage levels (+ 
> and - between 5 and 15V IIRC).
> TLL usually means that the signals are at the standard voltage of your 
> board (in the past 5V,now also 3.3V or 1.8V) even if sometimes it's used 
> to mean 5V.
> Obviously that means that you can't connect RS232 signals where TTL 
> signals are expected and vice-versa (communication will not work and you 
> may damage your hardware).
> You need a MAX232 or similar chip to convert voltage levels.
>
> -- 
> Valter Minute (eMVP)
> Training, support and development for Windows CE:
> www.fortechembeddedlabs.it
> My embedded programming and cooking blog:
> www.geekswithblogs.net/WindowsEmbeddedCookbook
> Windows Embedded support forums in Italian:
> http://social.msdn.microsoft.com/Forums/it-IT/windowsembeddedit/threads
> (the reply address of this message is invalid) 


0
Dean
3/25/2010 5:19:13 PM
Reply:

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