RS-232 signal inverter
RS-232 signalling, such as the MAX3323 generates, is bipolar, going both
above +3V, and below -3V, when fully loaded.   That MAX3323 chip has onboard generators for its power.   The inversion (positive input yields negative output)
is normal for RS-232 drivers (and receivers, which do a second inversion, at the other end).

If your target machine does not accept the  inverted signal, it is probably
intended for TTL-level drive with no MAX3323 intermediate required (and
won't work well with long connecting cables).   The MAX3323 can be omitted,
if this is the case.