From austin.green at ww.co.nz  Wed Jan 11 23:27:35 2006
From: austin.green at ww.co.nz (Austin Green)
Date: Thu, 12 Jan 2006 17:27:35 +1300
Subject: [Micro-VGA] RS232 and TTL signal levels
Message-ID: <3.0.5.32.20060112172735.007d6100@pop3.ww.co.nz>

Hi List,

I'm interfacing to a uVGA serial interface that uses TTL levels.
Does the TTL '1' level correspond to the RS232 +ve or -ve level?
My RS232/TTL converter chip inverts the signals, so I need to
know whether I have to add TTL inverters as well.

Regards,
Austin.



From neil at daveytronics.com  Wed Jan 11 23:47:05 2006
From: neil at daveytronics.com (Neil Davey)
Date: Thu, 12 Jan 2006 14:47:05 +1000
Subject: [Micro-VGA] RS232 and TTL signal levels
In-Reply-To: <3.0.5.32.20060112172735.007d6100@pop3.ww.co.nz>
References: <3.0.5.32.20060112172735.007d6100@pop3.ww.co.nz>
Message-ID: <43C5DF49.5020600@daveytronics.com>

The level on the RS232 side will be -ve for a TTL side logic 1

from http://www.beyondlogic.org/serial/serial.htm#1

1. 	A "Space" (logic 0) will be between +3 and +25 Volts.
2. 	A "Mark" (Logic 1) will be between -3 and -25 Volts.


If you are using a max232 or the like to interface from the serial port 
of a pc, you don't need any inverters

Regards
Neil Davey

Austin Green wrote:

>Hi List,
>
>I'm interfacing to a uVGA serial interface that uses TTL levels.
>Does the TTL '1' level correspond to the RS232 +ve or -ve level?
>My RS232/TTL converter chip inverts the signals, so I need to
>know whether I have to add TTL inverters as well.
>
>Regards,
>Austin.
>
>
>_______________________________________________
>Micro-VGA mailing list
>Micro-VGA at dontronics.com
>http://mail.dontronics.com/mailman/listinfo/micro-vga_dontronics.com
>
>  
>

-- 
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Daveytronics.com.au

P.O. Box 6089
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QLD, 4114

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From atilla at 4dsystems.com.au  Wed Jan 11 23:48:55 2006
From: atilla at 4dsystems.com.au (Atilla)
Date: Thu, 12 Jan 2006 15:48:55 +1100
Subject: [Micro-VGA] RS232 and TTL signal levels
In-Reply-To: <3.0.5.32.20060112172735.007d6100@pop3.ww.co.nz>
Message-ID: <003c01c61733$80f4b6d0$0202a8c0@atilla1>

Hi Austin,

TTL logic level '1' = RS232 -ve. No need to use additional inverters.


Regards,
Atilla 


-----Original Message-----
From: Micro-VGA-bounces at dontronics.com
[mailto:Micro-VGA-bounces at dontronics.com] On Behalf Of Austin Green
Sent: Thursday, 12 January 2006 3:28 PM
To: Micro-VGA at dontronics.com
Subject: [Micro-VGA] RS232 and TTL signal levels

Hi List,

I'm interfacing to a uVGA serial interface that uses TTL levels.
Does the TTL '1' level correspond to the RS232 +ve or -ve level?
My RS232/TTL converter chip inverts the signals, so I need to
know whether I have to add TTL inverters as well.

Regards,
Austin.


_______________________________________________
Micro-VGA mailing list
Micro-VGA at dontronics.com
http://mail.dontronics.com/mailman/listinfo/micro-vga_dontronics.com



From austin.green at ww.co.nz  Fri Jan 13 15:04:52 2006
From: austin.green at ww.co.nz (Austin Green)
Date: Sat, 14 Jan 2006 09:04:52 +1300
Subject: [Micro-VGA] RS232 and TTL signal levels - resolved
Message-ID: <3.0.5.32.20060114090452.007dd810@pop3.ww.co.nz>

Hi List,

Regarding my enquiry the other day: I have found by experiment
that the TTL '1' level corresponds to the RS232 -ve level.
The inverting RS232/TTL converter chip is the kind that works
most easily with the uVGA.

Regards,
Austin.