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Special Math Instructions Section 3-14
Description FDIV(079) divides the floating-point value in Dd and Dd+1 by that in Dr and
Dr+1 and places the result in R and R+1.
To represent the floating-point values, the rightmost seven digits are used for
the mantissa and the leftmost digit is used for the exponent, as shown in the
diagram below. The leftmost digit can range from 0 to F; positive exponents
range from 0 to 7 and negative exponents range from 8 to F (0 to –7). The
rightmost 7 digits must be BCD.
Two more examples of floating-point values are:
6123 4567: 0.1234567
× 10
6
(6 = 0110 binary)
B123 4567: 0.1234567
× 10
–3
(B = 1011 binary)
The following table shows the maximum and minimum values allowed.
Flags
Precautions The result is expressed as a floating-point value, so it has 7 significant digits.
The eighth and higher digits are eliminated.
The result must be between 0.1000000
× 10
–7
and 0.9999999 × 10
7
.
R+1 R
Quotient
Dr+1 Dr Dd+1 Dd
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
0: +
1: –
1 0 1 0 0 0 0 1 0 0 0 1 0 0 0 1
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
0 0 0 1 0 0 0 1 0 0 0 1 0 0 1 1
= 0.1111113 x 10
–2
mantissa (leftmost 3 digits)
First word
Second word
mantissa (rightmost 4 digits)
sign of exponent
exponent (0 to 7)
Limit 8-digit hexadecimal Floating-point
Maximum value 7999 9999
0.9999999 × 10
7
Minimum value
(Divisor and dividend)
F000 0001
0.0000001 × 10
–7
Minimum value
(Result)
F100 0000
0.1000000 × 10
–7
Name Label Operation
Error Flag ER ON if the mantissa (leftmost 7 digits) in Dd+1 and Dd is
not BCD.
ON if the mantissa (leftmost 7 digits) in Dr+1 and Dr is not
BCD.
ON if the divisor (Dr+1 and Dr) is 0.
ON if the result is not between 0.1000000 × 10
–7
and
0.9999999 × 10
7
.
OFF in all other cases.
Equals Flag = ON if the result is 0.
OFF in all other cases.
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