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

;-------------------------scale routine begins--------------------------+
; from BLUEBOOK OF ASSEMBLY ROUTINES FOR IBM PC & XT.
; page :173
; NAME SCALE
; ROUTINE FOR LINEAR SCALING
;
; FUNCTION: This routine performs a linear scaling, converting a fixed
; point number between 0 and 1 to an integer between X1 and X2, where
; X1 and X2 are 16-bit integers.
; INPUT: Upon entry CX has a binary fixed point number between 0 and
; 1. The binary point is to the left of the leftmost bit. X1 and X2 are
; variables stored in memory.
; OUTPUT: Upon exit CX contains the 16-bit integer result.
; REGISTERS USED: Only CX is modified.
; SEGMENTS REFERENCED: The data segment must contain the variables X1
; and X2.
; ROUTINES CALLED: None
; SPECIAL NOTES: None
;
; ROUTINE TO SCALE LINEARLY
;
scale proc far
;
push dx ; save registers
push ax
;
; compute width
mov ax,x2 ; get x2
sub ax,x1 ; subtract x1
;
; multiply width by input parameter
mul cx ; multiply
mov cx,dx ; move top part of quotient into CX
;
; add lower limit
add cx,x1 ; add x1
;
pop dx ; restore registers
pop dx
ret ; return
;
scale endp
;-------------------------scale routine ends---------------------------+