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IBM 7090 - Page 103

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To
execute
this
instruction,
an
E
cycle
is
required
to
bring
the
word
in
storage
to
the
storage
register;
then
an L
cycle
is
used
for
two
comparisons
in
the
adders.
For
the
first
comparison,
the
SR and
the
complement
of
the
AC
are
fed
to
the
adders;
the
Q
carry
and
sign
conditions
are
matched
to
condition
the
first
possible
skip.
The
sec-
ond
comparison
is
made
after
a one
has
been
added
to
the
difference,
to
differentiate
words
of
equal
magnitude.
The
following
illustrate
some
of
the
possible
combinations:
Number
in
Number
in
Q
Carry
Tgr
Accumulator
Storage
1st
Comp
2nd
Comp
Result
-6
-7
On
On
Next
Instruction
-6
-6
Off
On
Skip 1
Instruction
-6
-4
Off Off
Skip 2
Instructions
-6
+6
Off
On
Skip 2
Instructions
-0
+0
Off
On
Skip 2
Instructions
+0
-0
Off On
Next
Instruction
+6
-6
Off
On
Next
Instruction
+6
+4
Off
Off
Next
Instruction
+6
+6
Off
On
Skip 1
Instruction
+6
+7
On
On
Skip 2
Instructions
Logical
Compare
Accumulator
with
Storage
LAS -0340(1,
E,
L)
Figure
5.3-37
This
instruction
compares
the
contents
of
the
AC(P,
1-35)
with
the
logical
word
(S,
1-35)
stored
at
location
X.
The
sign
of
the
AC
is
disregarded;
the
contents
of
the
AC
and
storage
are
unchanged.
If
the
contents
of
the
AC
are
greater
than
the
contents
of
storage
location
X,
the
computer
takes
the
next
instruction
in
sequence.
If
the
AC
equals
storage,
the
computer
skips
one
instruction.
If
the
contents
of
the
AC
are
less
than
the
contents
of
storage,
the
computer
will
skip
the
next
two
instructions.
This
instruction
is
executed
the
same
as
CAS,
except
that
the
signs
are
not
used
for
an
algebraic
comparison
and
AC(P)
is
compared
against
SR(S).
Plus
Sense
PSE
+0760
...
XXXX(I, L)
This
instruction
provides
a
means
to
test
the
status
of
any
of
the
six
sense
switches,
to
turn
on
or
off
the
four
console
sense
lights,
and
to
permit
the
transmission
of an
impulse
to
or
from
the
exit
or
entry
hubs
of
either
the
printer
or
punch.
The
address
portion
of
the
instruction
determines
whether
a
light,
switch,
printer,
or
card
punch
is
being
sensed;
further,
it
determines'
which
light,
switch,
or
hub
is
being
sensed.
The
octal
addresses
for
the
different
sense
instructions
are:
Address
0140
0141-0144
Instruction
Turn
off
all
sense
lights
(Figure
5.3-38)
Turn
on
sense
light
1,
2,
3,
or
4,
respectively
(Figure
5.3-39)
102

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