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Do I need to invert the signals coming from the MAX232 chip?

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ericmar

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Hi all,

May I know if I need to invert the signals coming from the MAX232 chip? Does it convert -12V -> +5V, +12V -> 0V and vice versa? (ie. +5V -> -12V and 0V -> +12V)

Thanks a lot!

Regards,
Eric
 

Re: Regarding MAX232!

Have you ever looked at the datasheet???

There is a clear schematic representation on the TI MAX232 datasheet on page 2....and even lots of signal waveforms for R/T pins...


Yes...the buffers are inverting!!


Please do the minimum homework in the future (o;
 

Re: Regarding MAX232!

davorin said:
Have you ever looked at the datasheet???

There is a clear schematic representation on the TI MAX232 datasheet on page 2....and even lots of signal waveforms for R/T pins...


Yes...the buffers are inverting!!


Please do the minimum homework in the future (o;
Click to expand...
I did look at the datasheet before I post this question! Just that I'm not good at reading datasheets. :cry:

What I'm trying to ask is "Do I need to use an inverter IC or do the inversion in software before I pass the signals to a serial device?"

Thanks!
 

Re: Regarding MAX232!

ericmar said:
I did look at the datasheet before I post this question! Just that I'm not good at reading datasheets. :cry:
Click to expand...
reading datasheets are much easier than reading messages :!:
What I'm trying to ask is "Do I need to use an inverter IC or do the inversion in software before I pass the signals to a serial device?"
Thanks!
Click to expand...
short answer is no. you have not said anything about your circuit but assuming you have a conventional circuit (for example you want to connect your mcu to computer serial port) the answer is no you don't.
 

Re: Regarding MAX232!

eric,
with regards to your question regarding the need to invert signals from max232,i would like to say you need not do so.max 232 is a RS232
interface.In RS232 protocal, positive logic ranges from -3v to -25v and negative logic ranges from +3v to +25 v. to convert this to TTL compatible signals you need MAX232 or MAX233 if your PCB space is tight.

Now if you want to output any data through max232, you can do so
with the help of UART(16C450).
 

Regarding MAX232!

Remember that the signal is usally inverted two times, because you have two RS232 IC on each signal - one at the transmitting end and one at the receiving end.
When you invert the signal two times, it's the same as not inverting it at all.
 

Re: Regarding MAX232!

What I'm trying to ask is "Do I need to use an inverter IC or do the inversion in software before I pass the signals to a serial device?"
Click to expand...

If you want to connect your application to PC, why do you connect directly? How far does it take from your application to your PC?
 

Re: Regarding MAX232!

from pc serial port -9V come and is considered as logic 1 and +9v come and is considered as logic 0......

MAX 232 converts -ve voltage into +5v TTL and +ve voltage in 0 volts...as far as i have worked with it using PC interface...........
 

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