RCA 70/46 - Multiply (MER) (ME) (MDR) (MD)

Multiply
(MER) (ME)
(MDR) (MD)
General Description
Format
(RR Short)
(RX Short)
(RR Long)
(RX Long)
Condition Code
Interrupt Action
Floating-Point Instructions
• The operand in the floating-point register specified by the first address
(Rd is multiplied by the operand specified by the second address
(R
2
or XdB
2
/D
3
). The normalized product is loaded into the register
specified by the first address.
(MER) 3C
R1
R2
0
7 8
11
12 15
(ME) 7C
R1
X
2
B2
0
7 8 11 12
15 16 19
20
31
(MDR) 2C
R1 R2
0
7
8 11 12 15
(MD) 6C
R1
X
2
B2
0 7 8 11 12
15
16
19
20 31
•
Unchanged.
•
Address error:
Addressing (RX format).
Specification.
Exponent overflow.
Exponent underflow.
Notes • 1. The exponents of the two operands are added, and the sum is reduced
by 64 to form an intermediate exponent. The mantissas are normal-
ized
as described in the Add Normalize instruction, and multiplied
to form an intermediate mantissa. The intermediate mantissa is
then normalized (reducing its exponent by one for each digit left
shifted) to form the final product.
2. The sign of the product is determined by the rules of algebra.
3.
If the product mantissa is zero, the final product is made true zero.
4.
If the final product exponent is greater than 127, an exponent over-
flow
interrupt occurs.
5.
If final product exponent is less than zero, an exponer.t underflow
interrupt occurs.
6. For short operands, the low -order half of the register specified by
the first address is used in the calculation of the intermediate man-
tissa. The product mantissa has the full 14 digits as in the long
format and the two low-order digits are always zero.
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