Add Decimal
CAP)
General
Description
Format
(55)
Condition
Code
Interrupt Action
Notes
Decimal Arithmetic
Instructions
• The operand specified by
the
second address (B
2
/D
2
)
is added alge-
braically to
the
operand specified
by
the
first address
(Bt/D
1
).
The result
is stored in
the
field specified by
the
first address.
The
sign
and
the
magni-
tude
of
the
sum determine
the
condition code.
The operands can be variable
in
length up to 16 bytes
and
must
be
in
packed format.
If
operands overlap,
their
rightmost
byte location
must
coincide.
The addition
of
the
two operands can cause decimal overflow. Two
conditions which cause overflow
are:
0
•
•
1. a
carry
out
of
the
high-order position
of
the
result.
2.
a second operand
that
is
larger
than
the
first operand
and
significant
result positions
are
lost.
FA
I
Ll
I
L2
I
Bl
I
Dl
7
8 11
12
15
16 19
20
31
32
35
36
47
o -
sum
is zero.
1 - sum is less
than
zero.
2 -
sum
is
greater
than
zero.
3 - overflow.
Address
error:
Addressing.
Protection.
Data
error.
Decimal overflow.
• 1. High-order zeros
are
supplied
for
either operand
during
instruction
execution.
2.
All signs
and
digits
are
checked
for
validity.
3. The operand specified by
the
second address is unaltered.
4.
Processing is
from
right
to left.
5.
A zero result is always positive except when high-order digits
are
lost because of overflow.
In
overflow, a zero
result
has
the
sign
of
the correct result.
158
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