Agilent Technologies N1911A Programming Manual page 350

9 PSTatistic Subsystem
Error Messages
• If command is executed in other window besides CCDF window, error
• If there was no previously saved trace, error –221 "Settings conflict: No
322
–221 "Settings conflict: Requires CCDF window" occurs.
reference trace saved" occurs. Please check the status of saved reference
trace using command PST:CCDF:STOR:REF?.
N1911A/1912A P-Series Power Meters Programming Guide