Divide (Der) (De) (Ddr) (Dd) - RCA 70/46 Reference Manual

Divide
(DER) (DE) (DDR) (DO)
General Description
Format
(RR Short)
(RX Short)
(RR Long)
(RX Long)
Condition Code
Interrupt Action
Notes
Floating-Point Instructions
• The operand (dividend) in the floating-point register specified by the
first address (R
1 )
is divided by the operand divisor specified by the second
address (R 2 or XdB2/D3)' The
normalized
quotient is stored in the register
specified by the first address. The remainder is not retained.
(DER) 3D
R1 R2
0
7 8 11
12 15
(DE) 7D
R1
X 2
B2
0 7
8 11
12
15
16 19 20
31
(DDR) 2D
R1 R2
0 7
8
11
12 15
(DD) 6D
R1
X
2
B2
0 7
8 11
12 15 16 19 20
31
•
Unchanged.
•
Address error:
Addressing (RX fonnat).
Specification.
Exponent overflow.
Exponent underflow.
Divide error.
• 1. The exponents of the two operands are subtracted and the difference
is increased by 64 to form an intermediate exponent. The mantissas
are normalized as described in the Subtract Normalize instruction,
and divided to form the mantissa of the intermediate quotient. The
intermediate exponent and mantissa are normalized to form a final
quotient.
2. If the dividend (first operand) is zero, the quotient is made true zero.
3. If the divisor (second operand) is zero, a divide error interrupt
occurs.
4. The sign of the quotient is determined by the rules of algebra.
5. If the final quotient exponent is less than zero, the final quotient is
made true zero and an exponent underflow interrupt occurs.
6. If the final quotient exponent exceeds 127, an exponent overflow
interrupt occurs.
7. For short operands, the low-order halves of the registers are
unaltered.
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