MATH COPROCESSING

11.3.1.5Constant Instructions

Each constant instruction (see Table 11-5) loads a commonly used constant onto the stack. The values have full 80-bit precision and are accurate to about 19 decimal digits. Since a temporary real constant occupies 10 memory bytes, the constant instructions, only 2 bytes long, save mem- ory space.

Table 11-5. 80C187 Constant Instructions

FLDZ

FLD1

FLDPI

FLDL2T

FLDL2E

FLDLG2

FLDLN2

Load + 0.1

Load +1.0

Load

Load log2 10

Load log2 e

Load log10 2

Load loge 2

11.3.1.6Processor Control Instructions

Computations do not use the processor control instructions; these instructions are available for activities at the operating system level. This group (see Table 11-6) includes initialization, excep- tion handling and task switching instructions.

Table 11-6. 80C187 Processor Control Instructions

FINIT/FNINIT

FDISI/FNDISI

FENI/FNENI FLDCW FSTCW/FNSTCW FSTSW/FNSTSW FCLEX/FNCLEX FSTENV/FNSTENV

Initialize processor Disable interrupts Enable interrupts Load control word Store control word Store status word Clear exceptions Store environment

FLDENV FSAVE/FNSAVE FRSTOR FINCSTP FDECSTP FFREE

FNOP

FWAIT

Load environment Save state Restore state Increment stack pointer Decrement stack pointer Free register

No operation

CPU wait

11-6

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Intel 80C186XL, 80C188XL user manual C187 Constant Instructions, C187 Processor Control Instructions