Microsoft KB Archive/117865

= DOCERR: Control and Status Word Missing Abbreviation Info =

Article ID: 117865

Article Last Modified on 10/14/2003

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APPLIES TO


 * Microsoft Macro Assembler 6.11 Standard Edition

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This article was previously published under Q117865



SUMMARY
Page 148 of the "MASM 6.11 Reference Manual" has an alphabetical listing of math coprocessor instructions. Page 150 contains Figure 5.2, a diagram of the Control Word and Status Word. The manual is missing the descriptions of the different fields, which were included with the "MASM 6.0 Reference Manual."

The format of the Control-Word and Status-Word registers are as follows:

Control Word
Bit                                         Bit 15 14 13 12 11 10 9  8  7  6  5  4  3  2  1  0 X  X  X IC RC RC RC PC PC IE    PM UM ZM DM IM

Status Word
Bit                                         Bit 15 14 13 12 11 10 9  8  7  6  5  4  3  2  1  0 B C3 ST ST ST C2 C1 C0 ES SF PE UE OE ZE DE IE The abbreviations for the fields in the Control Word and Status Word are:   IC - Infinity Control 0 = Projective (default on 8087 and 80287) 1 = Affine Note: Used for 8087 and 80287 only, 80387 uses affine regardless of setting RC - Rounding Control 00 = Round to nearest or even (default) 01 = Round down toward -infinity 10 = Round up toward +infinity 11 = Chop by truncating toward 0 PC - Precision Control 00 = 24-bit mantissa 10 = 53-bit mantissa 11 = 64-bit mantissa IE - Interrupt Enable Mask Used for 8087 only; undefined on 80287 and 80387 SF - Stack Flag Used for 80387 only; undefined on 80287 and 8087

Exception Masks and Flags
  PM/PE - Precision UM/UE - Underflow OM/OE - Overflow ZM/ZE - Zero Divide DM/DE - Denormalized Operand IM/IE - Invalid Operation For masks: 1 = masked; 0 = unmasked

For exceptions: 1 = exceptions; 0 = no exception B - Busy 1 = exception control unit active

C3 C2 C1 C0 - Condition Codes

ST - Stack Top Pointer Points to current top of stack

ES - Error Summary (80287/387) On a 8087, the value is IR - Interrupt Request

Additional query words: 6.11

Keywords: KB117865

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