HP 8901B Operation And Calibration Manual page 154

Model
8901B
Operation
conditions.) The
- 1
block in the supervisor is where the hardware state is made to conform
with the software state.
The hardware state is the actual, current
state
of the internal settings of the instrument and is only
updated when enough time is allowed between commands for the Software Supervisor measurement
loop to be completed successfully without interruption; e.g., when a trigger is received.
blocks manipulate hardware as well and also
measurement. A measurement is not made
until all blocks are successfully completed in succession. If a block is not completed, a negative
decision after that block then forces the program back to the top of the supervisor,
measurement for that loop.
In a normal, stable measurement cycle, the program takes the
lhneasurement Display1
branch at the top
block. However,
exists, the
jNon-Measurement Display1
branch will be traversed. This will light an appropriate display, which is usually
''-
- -
-
",
and send the program back through the
1 - 1
block.
of the supervisor and so avoids the extra time associated with the
if the program loops back before taking a measurement, or if
After power-up, the external system controller can be thought of as a medium through which the user
requests a certain instrument setup which is first implemented in software state and then in hardware
state. Controller commands
( IKeyboard or HP-IB Interrupts1 )
are treated as non-returnable interrupts and
break the flow around the Software Supervisor loop, forcing the internal microprocessor to execute
a short program
to
change the software state and then return to the loop as shown in the diagram.
The commands applicable to the measurement mode are implemented in software state and then in
hardware state at the next
1 - 1 .
NOTE
Controller routines modify only the software state and do not affect the
hardware immediately.
Since a
]Keyboard or HP-IB Interrupti
can interrupt the Supervisor at any point
and return it
to
the point in the loop before
- 1 ,
these interrupts
abort the current measurement and start a new measurement cycle.
The actual instrument setup is guaranteed to conform to the Keyboard
request only at the moment
a
measurement is taken
(
P I ) .
3-35