HP 3455A - Page 35

Model 34SSA
Section 111
3-8t. Statdi Bytt M«t»
9
e.
The
status byte message is
output by the 34SSA in
response
to a serial poll and in-
dicates, to the controller, the nature of a
service
request
message (SRQ) from the
34SSA. The following
is a list
of the basic status byte codes output by the 34SSA;
Status Byte Code
ASCII
^ ,
CHAR
A
6S Data Ready
•
indicates to the con-
troller that rneasuremeni data
is
available. Applies
to
DATA
READY
Request feature.
B 66 Syntax Error
-
Indicates improper
1
program code. Example Pro-
gram
Code
"F7" would cause a
,
syntax error since the FUNC-
1
TION
program
set
is
only
defined
for codes FI through
F6.
D 68
1
'
BINARY FUNCTION Error
-
In-
dicates improper BINARY
PRO-
GRAM code or incomplete binary
message. Similar to syntax error.
H
!
72
Trigger too Fast
•
Indicates the
3455A has
been triggered while
measurement
data
is being
output
to the bus.
Warns
of
possible in-
correct measurement information.
it
is
possible for more than one of the basic
status
byte
messages to be
true. In this case the resulting status byte
code
would
be the
combinttuion
of the basic
status byte
codes being output. As an example, the resulting ct^e
for the combination of the syntax error and
trigger
too
fast
messages would be ASCII character J decimal code
74. The following illustrates the status Byte message in-
dicating
the purpose of each
relevant
"bit".
STATUS BYTE MESSAGE
3-B2. DATA OUTPUT CHAFIACTERISTICS.
3-83.
The protocol used by the 34SSA to output
measurement data must be followed in order to
preserve
proper data transfer over the HP-IB, the following
notes on
data transfer over the HP-IB
may
be helpful:
a. If a reading has been taken
and thus
resides in the
output buffer,
the buffer is not
considered busy until
the output
handshaking
begins. Thus, a
new
trigger
will
indicate a measurement and the
new
reading
will
replace
the old reading. The old reading is lost and there is no
SRQ
condition.
b. Once the Hrst character
of measurement data has
been
handshaken
out, the buffer is considered
busy
un-
til one of
the following
occurs:
1.
The
balance
of the
reading
is
handshaken out.
2.
“Device"
or "Selected
Device"
clear is
given.
3.
The
34SSA
power is
interrupted,
triggering
white
the buffer is busy
will lose the
new
reading and
cause
a
"Trigger
too Fast” SRQ
condition.
c.
When triggering and taking measurements in a
loop, sufficient time must be
allowed
for the 345SA to
perform the entire A-To-D measurement
cycle and buf-
fer data to become
available
after the first
reading. The
"Wait"
statements in many 9800 series calculators
are
convenient
methods to
avoid
outputting the
previous
buffer contents. This condition
shows
up as being "One
reading behind" in your measurement sequence.
d. If you
know
the output
buffer
is
not busy, but
don't
know whether
it is
full
or not,
sending
a
"device"
or selected device" clear followed by reprogramming
the desired conditions is a safe
way
to clear the output
buffer.
3-14. Bail Out MessagB.
3-15. Abort.
The Abort message
unconditionally ter-
minates all Bus communications and returns control to
the
system controller. Only the system controller can
send the Abort message. Refer to the
Operating Manual
of the controller being used for instruaions on
sending
the Abort Message.
3'BB.
Instrumont Mtaauroffloiit Timoi (Remots Control).
3-87.
In the Remote Operating
mode,
the
34SSA
takes
a
certain amount of time to respond to a trigger message.
The
overall time depends on the range, function, and
particular controller used. This time may also vary from
instrument to instrument. Table 3-6 gives the typical
measurement times, using the HP-IB. These times are
not part
of the operating specifications
of
the instru-
.'•l.l