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