Status Byte - HP 3456A Operating And Service Manual

Operation
line called the SRQ line. Its state is either true or false,
with low being true and high being false. When the Re­
quire Service Message is sent and more than one device
on the HP-IB has the capability to send this message,
the user must decide which device is sending the mes­
sage. This is done by conducting a "Serial Poll" for the
device(s) on the Bus. The device polled responds by sen­
ding a Status Byte. The Status Byte indicates whether
the device has requested service and if so, for what
reason. If the device polled shows that it did not send
the Require Service Message, the other devices would
typically be polled. Paragraph 3-140 describes the
3456A's Status Byte.
3-138. When the 3456A sends
Message. the front panel SRQ LED is on. The message
and LED are cleared when the 3456A is polled, although
some of the messages are cleared by the instrument (i.e.
Front Panel SRQ, Program Memory Complete, and
Data Ready). The following are the conditions that can
cause a Require Service Message.
Front Panel SRQ (can be cleared by the 3456A)
Program Memory Execution Complete (can be clear-
ed by the 3456A)
Data Ready (can be cleared by the 3456A)
Trigger Too Fast
Illegal Instrument State/Internal Error/Syntax Error
Program Memory Error
Limits Failure
3-139. The 3456A requires service only if told to do so.
lt has to be programmed to output the Require Service
Message for the previously listed conditions. This is
done by setting the Service Request Mask. The mask is
set by sending certain program codes to the 3456A and
is explained in Paragraph 3-169.

3-140_ Status Byte.

3 - 1 4 1 . The Status Byte Message is output by the 3456A
in response to a Serial Poll. Each bit represents a
message. Table 3-7 lists the bits which are defined as
follows.
NOTE
Remember to set the SRQ mask to output
the Require Service Message.
a. Front Panel SRO. A Require Service Message can
be output when pressing the 3456A's front panel SRQ
button. The button is only enabled in Local operation.
b. Program Memory Execution Complete. A Re­
quire Message is output when the 3456A's internally
programmed operation, called Program Memory. is
completed. Information on the Program Memory Oper­
ation is in Paragraph 3-200.
c. Data Ready. A Require Service Message is output
when the 3456A's measurement cycle is completed (e.g.
3-20
a DCV reading is taken). More information on Data
Ready is in Paragraph 3-206.
a Require Service
outPUI if the 3456A is triggered while outputting data
over the HP·IB. This can only be caused by the External
Trigger.
Error. This Message is output for the following condi­
tions:
Table 3·7. Status Byte Definition.
Octal Decimal
Bit
Code Code
1 0 1 6 5 F nt Panel SRO - When the front panel
o ro
SRO button
vice is output. Pressing the button a
cond
time
102 66 Program Memory Execution Complete
1
·Indicates to the controller that
program codes in the 3456A's internal
memory are executed. The Require Ser·
vice condition is cleared when the Pro­
gram Memory
104 68 2 Data
Ready - Indicates to the controller
that
measurement data is ready to be
output. The Require Service is cleared
when
a new measurement cycle is ini­
tiated.
1 1 0 72 3 Too Fast · Indicates that the
Trigger
3456A
was triggered while exe
measurement cycle.
External Trigger.
Ill l
1 2 0 8 0 4
ega Instrument
the 3456A
because of an invalid set·up le.g. 1 0 M
range in DCVI
ohm
Internal
Error
3456A
Syntax
Er
that invalid Program Codelsl where sent
to the 3456A (e.g. code F9)
140 96 5 Program
the Program Memory Execution com·
mand or the Test function was stored in
m m
e ory. or an overflow of memory oc­
curred while loading into memory.
300 1 9 2
limits Failure
7
Pass/Fail measurement made is out of
the selected limits.
6
Note: Bit is not in this table. because il is t
d . Trigger Too Fast. This Require Service Message is
e. Illegal Instrument State/Internal
I . Illegal Instrument State. An Illegal Instrument
State is when the 3456A is. for example, unable to
complete internal operations. An example is pro·
gramming the instrument to the 10 M ohm range
while in the DCV function. This range is invalid in
the DCV function.
2. Internal Error. An Internal Error occurs is when
a digital failure occurs in the 3456A. I f this may
Model 3456A
Oefinition
th Require Ser­
is pressed. is
se­
will clear the Service Request.
all the
is executed again.
t
c ing a
u
occurs in
This only
State · Indicates that
an operation
is unable to do
-
Indicates a failure in the
ro to the
r - Indicates controller
Indicates that
Memory Error -
- Indicates that the
h SRO bit.
e
Error/Syntax