HP 1650B Programming Reference Manual page 60

Each status register has an associated status enable (mask) register. By
setting the bits in the mask value you can select the status information you
wish to use. Any status bits that have not been masked (enabled in the
enable register) will not be used to report status summary information to
bits in other status registers.
Refer to appendix B for a complete discussion of how to read the status
registers and how to use the status information available from this
instrument.
Refer to figure 5-l for the common commands syntax diagram
= An integer, 0 through 255. 77zis number is the sum of all the bits in
mask
the mask corresponding to conditions that are enabled. Refer to the
Figure Common Commands Syntax Diagram
HP 1650B/HP 16518
Common Commands
Programming Reference
5 2