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Originally Posted by b3lha
I don't understand what you mean about RS232 and TTL voltages being compatible.:
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The TTL range is a subset of RS232.
Quote:
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Originally Posted by b3lha
In the data sheet for the M377xx CPU, it specifies the "Absolute Maximum Ratings" for the inputs for the UART pins as -0.3 volts to Vcc+0.3 volts. Vcc being 5 volts.
Would it not exceed the maximum rating by a factor of over 100% if your PC serial port supplied a 12 volt signal to these pins?  |
If the serial port was supplying the maximum RS232 of 12 volts (or is it 15?), it would exceed the limit for TTL devices. However, computers are TTL devices, too. There is no reason to expect that a computers UART is boosting the voltages above TTL or native levels. This would require lots of extra stuff which would add cost and heat and the only reason to do it would be to opperate over long distances. (on the order over 1/4 mile)
Charl