HP 54501A Programming Reference Manual page 75

4.
To check whether
bit 6
of
an instruments status
register is
high,
use
the
following command line.
IF BIT (Stat, 6)
then
5.
If bit
6
of the instrument
at address
1 is
not
high,
then check the
instrument
at address 7 to see
if
bit 6
of
its status register is high.
6.
As
soon
as
the instrument with
status
bit 6
high
is
found, check
the
rest
of the status
bits
to determine what
is
required.
The SPOLL(707)
command
causes much
more
to happen on the
bus than
simply reading the register. This command
clears the bus,
automatically
addresses the talker and listener, sends
SPE (serial poll enable)
and
SPD
(serial poll disable)
bus commands,
and reads the data.
For
more
information
about serial poll, refer to your controller manual, and
programming language reference manuals.
After
the serial
poll is
completed, the
RQS
bit in the
HP 54501A
Status
Byte Register will be reset if it was
set.
Once
a
bit
in
the Status Byte
Register
is set, it will remain
set
until the
status is cleared
with
a
*CLS
command, or the instrument
is
reset.
If
these bits
do not get reset,
they
cannot generate another SRQ.
HP 54501A
Message Communication and System Functions
Programming
3-33