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IEEE-488 Programming
Programming
notes
U7
Digital
input
The
U7 command
(Figure 5-22) requests a
decimal value of
the inputs
at
the
digital
I/O
port.
In
master/slave configurations,
the
digital
input
of
the
master
unit
is
sent.
Id entifi
er
DINiii,<TERM+EOf>
'
Input
(000-255)
Figure 5-22
U7
digital
input
U8
Relay
Test input
The
U8 command
(Figure 5-23) requests the
status
of
the input pins
at
the
Relay
Test connector.
Values
between 0 and
15 represent the
status
of
pins
1
(LSB)
through
4 (MSB).
identifier
h
RTI nn
<TERM+EOI
>
Pins
1
Through 4
(0-150)
Pin
1
is
LSB
Figure 5-23
U8
relay
test
input
1.
The
instrument
transmits
the
appropriate
status
word
only once each time
the
corresponding
U
command
is
received.
2.
To
ensure
that
correct
status
is
indicated, the status
word
should
be
requested
immediately
after
the
command
is
transmitted.
The
status
sent
by
the
Model
707A
is
that
which
is
present
at
the
time
it
is
instructed
to talk,
not
at
the
time
the
U
command
is
received.
3.
The
bits in
the
U1
emor
status
word
latch
and remain
in
that
condition
until
the
U1 word
is
read.
4.
The programmed
terminator
(default
CR
LF)
is
transmitted
at
the
end of
each
status
word.
Also,
EOI
is
transmitted
at
the
end
(unless disabled
with
the
K
command).
5.
If
no
U
command
has been
received, the
PRINT
#1,
"ENTER
18" and
LINE INPUT
#2,
A$
commands
request
the
letter
(x)
and
number
(nn)
of
the software revision for a
stand-alone
unit
or the
master
unit
of
a master/slave configuration
(707Axnn).
It is
sent
with
two
trailing
spaces plus
the
terminator
and EOI.
5-38
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