Technical data

is good technique, then, to periodically poll the OPC bit to determine if the
overlapped command has completed.
• *WAI
The *WAI command allows no further execution of commands or queries until
the No Operation Pending flag is true, or receipt of a Device Clear (dcas)
message, or a power on.
The *WAI command can be used for overlapped commands. It stops the
program execution until any pending overlapped commands have finished.
Specifically, it waits until the No Operation Pending flag is TRUE, or receipt of
a dcas message, or a power on.
• *OPC?
The *OPC? query returns the ASCII character "1" in the Output Queue when
the No Operation Pending flag is TRUE. At the same time, it also sets the
Message Available (MAV) bit in the Status Byte Register. The *OPC? will not
allow further execution of commands or queries until the No Operation Pending
flag is true, or receipt of a Device Clear (dcas) message, or a power on.
N O T E
The command behaviors described above are for overlapped commands. When the
same commands are used with sequential commands, the behaviors may be
different.
For the Serial BERT, six conditions can change an operation pending flag. Notice
that the first four correspond to the four overlapped commands:
• The automatic eye-time-centering operation has expired.
• The automatic eye-amplitude-centering operation has expired.
• An automatic alignment has occurred.
• The requested operation failed.
• The operation was aborted by the user.
Data Types
The Serial BERT has the capability of receiving and returning data in the following
formats:
• STRING
A string of human-readable ASCII characters, either quoted or non-quoted.
• NUMERIC
The Serial BERT handles three numeric formats:
– <NR1>: Integer (0, 1, 2, -1, etc.)
SCPI Command Language 4
Agilent J-BERT N4903B High-Performance Serial BERT 81
Operation Pending Events