Is it possible to terminate the carrier signal at the zero crossing using a Maxim DS8500 HART modem?
It appears that if this is not done, the glitch at the end of the carrier gets interpreted as extra 0xFF’s which causes a communication error to occur. This is required for HART test certification. Please see attached waveform. The RTS (request to send) line is the yellow trace, the carrier is in purple, and the RS-232 received data on the test modem is in blue. The glitch is located at the very end of the carrier waveform.