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Model8672A
Operation
3-40. Sending Data
Messages
3-41. The Synthesizer
sends
a
status
byte when
addressed
to talk. This byte
is
the Synthesizers
response
to
a
serial
poll which
will
be
explained
in
paragraph
3-59.
The Synthesizer will talk when
in
local
as
well
as
remote.
3-42.
Receiving the Trigger Message
3-43. The
Synthesizer doesn't respond to the
Trigger message.
3-52.
Receiving
the
Clear
Lockout/Set
Local
Message
3-53. The
Synthesizer
responds
to
the
Clear
Lockout/Set
Local
message in
the
same
way
as
to
the Local
message
(that
is,
it
returns to local). The
Synthesizer
need
not
be addressed
to
listen.
This
message sets
the
REN
line false.
3-54.
Receiving
the
Pass
Control
Message
3-55. The
Synthesizer does
not
respond to the
Pass
Control
message
as
it
cannot
act
as
a
controller.
3-44. Receiving the Clear
Message
3-45. The
Synthesizer
responds
to
the
Clear
message
by setting the frequency to
3
GHz, ALC
to internal,
RF
power off,
and
modulation off.
This
message can
take two forms: Device Clear,
which the Synthesizer
responds
to
when not
ad¬
dressed,
and
Selected
Device
Clear which
the
Synthesizer
responds
to
when
addressed
to
listen.
The
Device Clear
messages
do
not affect
addressing.
3-46. Receiving the Remote
Message
3-47.
The Synthesizer
is
enabled to
go
into remote
when
the
controller
sends
the
Remote
message,
but
does
not
actually switch to
remote until first
ad¬
dressed
to
listen.
The Remote
message
is
the
means
by which the controller
sets
the remote enable line
(REN)
true. Some controllers
send
this message
automatically when first turned
on or reset.
3-48.
Receiving the Local Message
3-49.
The
Synthesizer returns to local
front
panel
control when it
receives
the Local
message.
The
frequency will not
change
from the
last program¬
med value but the other functions will correspond
to the
front
panel control
settings.
3-50.
Receiving
the Local Lockout
Message
3-51. The Synthesizer
does
not
respond to the
Local
Lockout
message.
STATUS BYTE
3-56.
Sending the Require Service
Message
3-57. The Synthesizer
sends
the Require Service
message
to the
controller when one of the follow¬
ing conditions exists
for
more than
50
ms:
1)
Not
phase-locked
with
RF
power
on.
2)
Frequency programmed out of
range.
3)
RF
power
level
uncalibrated
with
RF
power
on.
4)
FM
overmodulated with
RF
power on.
The
Synthesizer
sends
this
message
by setting the
service
request line
(SRQ)
true.
It
will
request
service in local or
remote whether
or
not it
is
addressed.
3-58. Sending
the Status Byte Message
3-59. The Synthesizer
sends
the
status
byte when
addressed
to talk. This
byte
is
the Synthesizer's
re¬
sponse
to
a
serial poll.
The Synthesizer responds to
a
serial
poll when the controller
sends
a
serial
poll
enable command
(SPE), then
addresses
the
Synthe¬
sizer
to talk. The
SPE
command
enables
the
Synthesizer to clear the
service request
(SRQ)
when
addressed
to talk. Also, when the Synthesizer
re¬
ceives its
talk
address,
bit
7
of
the
status
byte
is
latched. The Controller
can then
determine the
status
of
the Synthesizer
by
converting the
status
byte
to
a
decimal value. Status
byte
coding
is
as
follows:
Bit
Number
Decimal Value
Function
8
128
CRYSTAL
OVEN
COLD
7
64
RSV
REQUEST
SERVICE
6
32
OUT OF
RANGE
(frequency)
5
16
RF
OFF
4
8
NOT
PHASE
LOCKED
3
4
LEV
UNCAL
2
2
FM
OVER-
MOD
1
1
+10
dBm
OVER-
RANGE
3-19
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