This enables or disables ATM cell payload scrambling on this physical port. Payload scrambling prevents long runs of repetitive bit patterns in cell payloads from mimicking framing patterns, so a mismatch of this setting against the far end of this specific ATM link causes cell delineation errors that look like random bit errors rather than an obvious misconfiguration. If this port is enabled for scrambling but the connected ATM switch on the other end has it disabled, you would expect this port's HCS or cell-sync error counters to climb even though the physical signal is clean.