TS68882
Packed Decimal String
Real Data Format
The packed decimal string data format allows packed BCD strings to be input to and
output from the TS68882. The strings consist of a 3-digit base 10 exponent and a 17-
digit base 10 mantissa. Both the exponent and mantissa have a separate sign bit. All
digits are packed BCD, such that an entire string fits in 96 bits (three long words). As is
the case with all data formats, when packed BCD strings are input to the TS68882, the
strings are automatically converted to extended precision real values. This allows
packed BCD numbers to be used as inputs to any operation. For example:
FADD.P # - 6.023E + 24, FP5
BCD numbers can be output from the TS68882 in a format readily used for printing by a
program generated by a high-level language compiler. For example:
FMOVE.P FP3.BUFFER (# -5)
instructs the TS68882 to convert the floating-point data register 3 (FP3) contents into a
packed BCD string with five digits to the right of the decimal point (FORTRAN F format).
Data Format Summary
All data formats described above are supported orthogonally by all arithmetic and tran-
scendental operations, and by all appropriate TS68000 Family addressing modes. For
example, all of the following are legal instructions:
FADD.B
FADD.W
FADD.L
FADD.S
FADD.D
FADD.X
FADD.P
# 3.FP0
D2.FP3
BIGINT.FP7
# 3.14159.FP5
(SP) + .FP6
[(TEMP -PTR.A7)].FP3
# 1.23E25.FP0
On-chip calculations are performed to extended precision format, and the eight floating-
point data registers always contain extended precision values. All data used in an oper-
ation is converted to extended precision by the TS68882 before the specific operation is
performed, and all results are in extended precision. This ensures accuracy without sac-
rificing performance.
Refer to Figure 17 for a summary of the memory formats for the seven data formats sup-
ported by the TS68882.
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2119A–HIREL–04/02
ATMEL [ ATMEL ]
