80C187 Datasheet, PDF (4/30 Pages) Intel Corporation – 80-BIT MATH COPROCESSOR

80C187
Numeric Operands
Register Set
A typical NPX instruction accepts one or two oper-
ands and produces one (or sometimes two) results
In two-operand instructions one operand is the con-
tents of an NPX register while the other may be a
memory location The operands of some instructions
are predefined for example FSQRT always takes
the square root of the number in the top stack ele-
ment (refer to the section on Data Registers)
Figure 2 shows the 80C187 register set When an
80C187 is present in a system programmers may
use these registers in addition to the registers nor-
mally available on the CPU
DATA REGISTERS
80C187 computations use the extended-precision
real data type
Table 1 Data Type Representation in Memory
NOTES
1 S e Sign bit (0 e Positive 1 e Negative)
2 d_n e Decimal digit (two per byte)
3 X e Bits have no significance 80C187 ignores when loading zeros when storing
4 U e Position of implicit binary point
5 I e Integer bit of significand stored in temporary real implicit in single and double precision
6 Exponent Bias (normalized values)
Single 127 (7FH)
Double 1023 (3FFH)
Extended Real 16383 (3FFFH)
7 Packed BCD (b1)^S (D₁₇ D₀)
8 Real (b1)^S (2^E-BIAS) (F₀ F₁ )
4
270640 – 2