Datron 4708 User Handbook Manual page 53

A
series
of
these
commands
can be
sent together as
a
'program
string', each programming
instruction being
position-depend-
ent.
Each
string will contain
at least
one programming
instruction
(detailed
later in this section), but the
4708 must
receive the
string
'terminator' before
it
can
activate
any
instructions.
The
required terminator
for
the4708
is
either the
ASCII
character
*='
or
EOI
asserted coincident with
the
line
feed character (decimal
10
).
R4F301 =
.
i
.
r
string
e.g.
programming
terminator
instructions
To
assist in eliminating
incorrect
programming
instructions, the
4708
checks
for errors
in the
string,
and
generates a service
request
(SRQ)
if
a syntax
error occurs or
if
an
option
is
called
for
but not
fitted.
To
ensure
that
the
programming
string
does
not
set
up
a prohibited
state,
it
also
checks
the
whole
string for
validity. If
it
finds
any
errors
in this phase, the
whole
command
string
is
ignored.
For Example:
With
the
4708
set in
lOmV
Range, a
string
is
received
which
contains an unacceptable
command
to
switch
Sense
connection
('S'
command). The
user needs
to set
up
a completely new,
valid
string:
so the
whole
string
is
discarded.
Device-dependent
commands
To
give
maximum
scope
for system programming,
the
bus
operation
of
the
4708
differs in detail
from manual
operation,
which
is
organised
for ease of
front
panel
use.
Some
functions
of
the
4708 firmware
are deleted for bus
operation, as they are
easily
programmed
into the system
controller;
and
extra func-
tions
have been made
available
to take
advantage of
the
control-
ler's
added computing
power.
The
following Alphabetic codes
are
used
to
establish the
re-
quired functioning
of
the
4708
as a
calibration source:
Full Range/Zero:
A
Safety
Delay
Override:
D
Output
ON/OFF: O
Function
DCV, ACV,
DCI, ACI, Q: F
Output
Range
in
all
Functions:
R
Output Value:
M
Frequency:
H
Spot
Frequencies:
T
Sense:
S
Guard:
G
'Calibrate'
trigger:
C
Calibration
Mode
Enable:
W
The
following Alphabetic codes
are
used
to select
and
configure
the messages
to
be passed by
the
4708
via the
IEEE
Bus:
User memory
I
Output
string terminators:
K
Notation of output
values:
L
Specification tolerances
(relative:
per
unit):
P
Specification tolerances
(absolute
limits):
U
RecallA^erify
(relative):
V
Service request
origination:
Q
Diagnostic information:
X
Table
5.4
lists
the
range of device-dependent command
codes
available.
Fig. 5.3 summarises
the
way
that front panel
functions
are
transferred
to
system
operation.
5-5