piclist 2001\01\22\141617a >
Thread: Better way for rs232 - Resistors or MAX202?
face BY : Dan Michaels email (remove spam text)

At 10:10 AM 1/22/01 -0800, you wrote:
>I know this might have been asked before, but I was unable to find it in
the list archive.  What is they better way to setup a serial port?  Lots of
schematics use the MAX202 or MAX232 to transmit the serial data, while
others just use a resistor on the RX and TX line.  Is there any particular
advantage to either way?  The resistors would be easiest, since I could just
run up to Radio Shack for those, but I don't know much about PICs or EE.

MAX-type chips - best approach, if rigorously meeting the specs is

BJT-inverter type ckts - generally acceptable, but +V usually = 5v,
 rather than +12v. Better ckts use a half-wave rectifier on the
 Rxd line to develop/hold -12v.

Simple R ckts - very slap-dash [IMO], neg-voltages especially are
 typically out-of-spec.

hope this helps,
- Dan Michaels
Oricom technologies

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See also: www.piclist.com/techref/io/serials.htm?key=rs232
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