Siemens CPU 948 - Page 136

DED The value in ACCU 1 (bits 0 to 31) is interpreted as a BCD number. After
the conversion, ACCU 1 contains a 32-bit fixed point number.
DUD The value in ACCU 1 (bits 0 to 31) is interpreted as a 32-bit fixed
point number. After the conversion, ACCU 1 contains a BCD number.
31 30 0
S2
30
. . . . . . . . . 2
0
DUD ↓ DED ↑
31
0
S S S S 10
6
10
5
10
4
10
3
10
2
10
1
10
0
S (sign): 0 = positive
1 = negative
FDG The value in ACCU 1 (bits 0 to 31) is interpreted as a 32-bit fixed
point number. After the conversion, ACCU 1 contains a floating point
number (exponent and mantissa).
GFD The value in ACCU 1 (bits 0 to 31) is interpreted as a floating point
number. After the conversion, ACCU 1 contains a 32-bit fixed point
number.
31 30 0
S2
30
. . . . . . . . . 2
0
FDG ↓
GFD ↑
31 30 ... ... 24 23
0
S2
6
. . . . . . . . . . . . . . 2
0
S2
-1
. . . . . . . . . . 2
-23
Exponent Mantissa
The conversion is made by multiplying the (binary) mantissa by the value
of the (binary) exponent by shifting the mantissa value to more significant
bits past an imaginary decimal point by the value of the exponent (base
2). After the multiplication, remnants of the original mantissa remain to
the right of the imaginary decimal point. These bit places are cut off from
the whole result.
Executive Operations
CPU 948 Programming Guide
3 - 64 C79000-G8576-C848-04