bit 0 RDV (result data available)
set when results are available to be read as
enabled by DAVER
bit 3 ALA (alarm active)
set when an alarm is active and enabled by
ALARMER
bit 4 MAV (message available)
set when a message reply is waiting to be read
bit 5 ESB (standard event summary bit)
set if any bit in the standard event status
register is set as well as the corresponding bit
in the standard event status enable register
(set by *ESE).