USRobotics V.34 - Manual (Page 122)

COURIER HIGH SPEED MODEMS
B-28 Summaries and Tables
Register Default Function
S55 0 Trellis code bit-mapped register used
primarily by U.S.Robotics Technical
Support for debugging purposes.
S56 0 Bit-mapped register primarily used
by U.S.Robotics Technical Support for
debugging purposes.
Bit 6 (ATS56.6=1) disables V.34
modulation.
Bit 7 (ATS56.7=1) disables V.FC
modulation.
S57 0 Reserved for German operations.