Computer Hardware User Manual

238
5-19-13 FLOATING POINT DIVIDE – FDIV(79)
Dd: First dividend word (BCD)
IR, SR, AR, DM, HR, TC, LR
Dr: First divisor word (BCD)
IR, SR, AR, DM, HR, TC, LR
Ladder Symbols
Operand Data Areas
R: First result word
IR, SR, AR, DM, HR, LR
FDIV(79)
Dd
Dr
R
@FDIV(79)
Dd
Dr
R
Limitations Dr and Dr+1 cannot contain zero. Dr and Dr+1 must be in the same data area, as
must Dd and Dd+1; R and R+1.
The dividend and divisor must be between 0.0000001 x 10
–7
and
0.9999999 x 10
7
. The results must be between 0.1 x 10
–7
and 0.9999999 x 10
7
.
Description When the execution condition is OFF, FDIV(79) is not executed. When the
execution condition is ON, FDIV(79) 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.
R+1 R
Quotient
Dd+1 DdDr+1 Dr
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 below. The
mantissa is expressed as a value less than one, i.e., to seven decimal places.
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
First word
exponent (0 to 7)
sign of exponent 0: +
1: –
1010000100010001
mantissa (leftmost 3 digits)
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
Second word
mantissa (leftmost 4 digits)
0001000100010001
= 0.1111111 x 10
–2
Flags ER: Dr and Dr+1 contain 0.
Dd, Dd+1, Dr, or Dr+1 is not BCD.
The result is not between 0.1 x 10
–7
and 0.999999 x 10
7
.
Indirectly addressed DM word is non-existent. (Content of DM word is
not BCD, or the DM area boundary has been exceeded.)
EQ: ON when the result is 0.
BCD Calculations Section 5-19