83 lines
3.1 KiB
NASM
83 lines
3.1 KiB
NASM
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; Copyright (C) Microsoft Corporation, 1986
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;
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; This Module contains Proprietary Information of Microsoft
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; Corporation and should be treated as Confidential.
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;
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subttl emdoc.asm - Documentation
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page
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;--------------------------------------------------------------------
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;
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; WARNING - This may not be accurate for the stand-alone emulator.
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;
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; Glossary:
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; TOS - top-of-stack (e.g. simulated 8087 register stack)
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; single - single precision real number in one of two formats:
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; memory (IEEE), internal (on stack, see below)
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; double - double precision real number in one of two formats:
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; memory (IEEE), internal (on stack, see below).
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;
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; This source is organized into the following sections:
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; 1. Introductory documentation of instructions and data structures
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; 2. External routines, data segment, and const segment definitions
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; 3. Startup and terminate, utility truncTOS
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; 4. User memory macros
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; 5. Macros and procedures for stack push and pop, error handling
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; 6. Main entry point and effective address calculation routine
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;
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; Assumptions about segment usage:
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; SS = user's stack
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; DS = user's emulator data segment (not user's DS)
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; ES = effective address segment for memory operands
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; = user's emulator data segment (all other times)
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;
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; BASstk is DS offset of the stack base
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; CURstk is DS offset of the current register (TOS).
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; LIMstk is DS offset of LAST reg in stack
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;
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; CURerr has internal exception flag byte (<>0 iff exception occured).
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; UserControlWord has user set values
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; ControlWord has remapped version of UserControlWord
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; CWcntl (high byte of ControlWord) has Rounding, precision, Inf modes
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;
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; Macros:
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; PUSHST allocates a new 12 byte register, and POPST frees one.
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; Both return an address in SI and save all other 8086 registers.
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;
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; Five macros handle all data movement between user memory and local
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; memory or registers.
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;
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; Note standard forms:
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;
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; Bits are counted from least significant; bit 0 is 1's, bit 7 is 128's.
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;
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; IEEE format is used, naturally, for values in user memory:
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;
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; IEEE single precision:
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; +0: least significant byte of mantissa
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; +1: next sig. byte of mant.
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; +2: bits 6..0: most sig. bits of mant.
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; +2: bit 7: low order bit of exponent
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; +3: bits 6..0: rest of exponent
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; +3: bit 7: sign bit
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; mantissa does not include "hidden bit".
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; with hidden bit, mantissa value is 1.0 to 2.0
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; exponent is in biased form, with bias of 127
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; exponent of all 0's means a value of zero
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; exponent of all 1's means a value of "indefinite"
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;
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; IEEE double precision:
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; +0: least significant byte of mantissa
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; +1..+5 next sig. bytes of mant.
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; +6: bits 3..0 (lo nibble): most sig. bits of mant.
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; +6: bits 7..4 (hi nibble): least sig. bits of exp.
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; +7: bits 6..0: most sig. bits of exponent
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; +7: bit 7: sign bit
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; mantissa does not include "hidden bit".
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; with hidden bit, mantissa value is 1.0 to 2.0
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; exponent is in biased form, with bias of 1023
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; exponent of all 0's means a value of zero or Denormal
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; exponent of all 1's means a value of NAN or Infinity
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