Category : Assembly Language Source Code
Archive   : ASM-SUBR.ZIP
Filename : SFP2DFP

;-------------------------sfp2dfp routine begins--------------------------+
; ROUTINE FOR CONVERSION FROM SINGLE PRECISION TO DOUBLE PRECISION
;
; from BLUEBOOK OF ASSEMBLY ROUTINES FOR IBM PC & XT.
; page : 111
;
; NAME SFP2DFP
;
; FUNCTION: This routine converts from single precision binary floating point
; to internal double precision floating point.
;
; INPUT: Upon entry a number is stored in single precision binary floating
; point form in SFPBUFF. The single precision binary floating point number
; has a 24-bit binary mantissa, a sign bit, and an 8-bit exponent biased by
; 128 (See fig 5-3).
;
; OUTPUT: Upon exit a internal double precision binary floating point
; number is stored in DFPBUFF. The internal double precision floating point
; number has a 40-bit binary mantissa, a sign bit,and an 8-bit exponent
; biased by 128 (See fig 5-8).
;
; REGISTERS USED: No registers are modified.
;
; SEGMENTS REFERENCED: Upon entry the data segment must contain the
; storage for the variables SFPBUFF and DFPBUFF.
;
; ROUTINES CALLED: None
;
; SPECIAL NOTES: Equates are used to shorten address fields.
;
; ROUTINE TO CONVERT FROM INTERNAL SINGLE PRECISION FLOATING POINT TO
; INTERNAL DOUBLE PRECISION FLOATING POINT
;
sfp2dfp proc far
;
push ax ; save registers
;
; clear lower part of mantissa
mov dfpbuffw0,0 ; clear low word
mov dfpbuffw2,0 ; clear next low word
;
; move rest of mantissa
mov ax,sfpbuffw0 ; get word from single precision
mov dfpbuffw4,ax ; put in double precision
;
mov ax,sfpbuffw2 ; get word from single precision (7 hi bits)
mov dfpbuffw6,ax ; put in double precision
;
pop ax ; restore registers
ret ; return
;
sfp2dfp endp
;-------------------------sfp2dfp routine ends---------------------------+