A59 Digital Interface Assembly - HP 8340B Manual

A59 DIGITAL INTERFACE ASSEMBLY
The
digital
interface
links
the instrument
processor
to the
sweep generator, the reference M/N
oscillator, and the
20-30
synthesizer.
Read/Write Strobes
The instrument processor read/write strobes enable
buffers
that either send data to the
instrument
processor, or clock registers that store data sent from the instrument processor. Several strobes also
operate registers on other assemblies.
Low Stop (LSTP) and Low Service Request (LSRQ)
The
digital interface
assembly connects
to the 16-bit
data
bus (DBO
to DB15). Using the
LSTP
(low
stop) signal, this assembly
can stop
all
instrument processor
operations when
all
current tasks are
completed. When the instrument processor stops, the
RUN LED on the processor assembly turns
off.
LSTP stops the instrument processor when it
is
not
needed, or
when
it is
necessary
to eliminate
all
potential sources of digital noise (e.g. during forward sweeps).
When the
LSTP signal
releases the instrument processor to perform
a
task, the instrument processor
defers processing
until it determines that
the
LSRQ
(low
service request) signal
is
low.
LSRQ
can be
sent low by the digital interface, by the front panel interface, or by LBX (low bandcross). Once LSRQ
is
sensed
low,
it
can
go high
again; the instrument processor finishes all
pending tasks before checking
this signal
again.
Controller Response
Using the change detectors and the processor service request block, the
instrument processor
responds to the
Following:
•
Changes in the
UNLOCK or OVEN
indicators
•
Changes in
OVERMOD
or
UNLEVELED
conditions
•
Changes
in
the
EXTERNAL REFERENCE
switch
position
• Sweep
events
as indicated by the marker/bandcross
assembly
The
instrument processor also distinguishes between power on and instrument preset.
F-4
Controller Section Theory of Operation
HP 8340B/41B