Xerox 560 Reference Manual page 90

DM
DECIMAL MULTIPLY
(Byte index alignment, continue after interrupt)
If no illegal digit or sign is detected in the effective decimal
operand or decimal accumulator, DECIMAL MULTIPLY
multiplies the effective decimal operand (multiplicand) by
the contents of the decimal accumulator registers R14 and
R15 (multiplier) and then loads the product into the entire
decimal accumulator.
If
the result in the decimal accumu-
lator is zero, the resulting sign is forced to the positive form.
Affected: {DECA}, CC
(DECA) x EDO - DECA
Condition code settings:
2 3 4 Result in DECA
Trap: Decimal arithmetic
o
Illegal di git or sign detected, instruction
aborted
o
0 0 0 Zero
J
N
·,1 I
d· . t .
o I ega Igl or sign
o
0 0 Negative detected, instruction
O P
.. completed
o
0 oSltlve
DD
DECIMAL DIVIDE
(Byte index alignment, continue after interrupt)
If
there is no illegal digit or sign in the effective decimal
operand and
if
there is at least one decimal sign in the
decimal accumulator, DECIMAL DIVIDE divides the con-
tents of the decimal accumulator (dividend) by the effec-
tive decimal operand (divisor). Then,
if
no overflow has
occurred, the basic processor loads the quotient (15 decimal
digits plus sign) into the eight low-order bytes of the
decimal accumulator (registers 14 and 15), and loads the
remainder (also 15 decimal digits plus sign) into the eight
high-order bytes of the decimal accumulator (registers 12
and 13). The sign of the remainder is the same as that of
the original dividend. If the quotient is zero, the sign of
the quotient is forced to the positive form.
Overflow occurs if any of the following conditions are not
satisfied before the initial execution of DECIMAL DIVIDE:
1.
The divisor must not be zero.
2. If the length of the dividend is greater than 15 decimal
digits, the absolute value of the significant digits to
the left of the 15th digit position (i. e., those digits in
registers 12 and 13) must be less than the absolute value
of the divisor.
Affected: (DECA), CC
(DECA) .;- EDO - DECA
84 Decimal Instructions
Trap: Decimal arithmetic
Condition code settings:
2 3 4 Result in DECA
0
-
Illegal digit or
J
sign detected
Instruction aborted
0 Overflow
0 0 0 0 Zero quotient
No illegal digit or
0 0 0 Negative quotient
sign detected, no
overflow, i nstruc-
0 0 0 Positive quotient
tion completed
DC
DECIMAL COMPARE
(Byte index alignment)
If there is no illegal digit or sign in the effective decimal
operand or in the decimal accumulator, DECIMAL COMPARE
expands the effective decimal operand to 16 bytes (31 digits
plus sign) by appending high-order O's, algebraically com-
pares the expanded decimal number to the contents of the
entire decimal accumulator, and sets CC3 and CC4 accord-
ing to the result of the comparison (a positive zero compares
equal to a negative zero).
Affected: CC Trap: Decimal arithmetic
(DECA) : EDO
Condition code settings:
2 3 4 Result of comparison
o
Illegal digit or sign detected, instruction
aborted
0 0 0 0 (DECA) equals EDO 1
No
i!
lega! digit
0 0 0 (DECA) less than EDO
)
or sign detected,
instruction
0 0 0 (DECA) greater than
completed
EDO
DSA
DECIMAL SHIFT ARITHMETIC
(Byte index alignment)
If
no illegal digit or sign is detected in the decimal accu-
mulator, DECIMAL SHIFT ARITHMETIC arithmetically shifts
the contents of the decimal accumulator (excluding the
decimal sign), with the direction and amount of the shift
determined by the effective virtual address of the instruc-
tion.
If
the result in the decimal accumulator is zero, the
resulting sign remains unchanged.