HP 54501A - 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