Category : Files from Magazines
Archive   : VOL9N1.ZIP
Filename : INIT87.ASM

title INIT87.ASM Initialize Numeric Coprocessor
page 55,132

; INIT87.ASM Initialize 80x87 Numeric Coprocessor
;
; Copyright (C) 1989 Ziff Davis Communications
; PC Magazine * Ray Duncan
;
; Call with: AX = control word for desired rounding
; mode, precision, exception mask
;
; Returns: (if coprocessor present)
; Z flag = True (1)
;
; (if coprocessor not found)
; Z flag = False (0)
;
; Destroys: nothing

_TEXT segment word public 'CODE'

assume cs:_TEXT

public init87
init87 proc near

push bx ; save registers
push ax

mov ax,-1 ; put FFFFH on stack
push ax
mov bx,sp ; make it addressable

fninit ; try to initialize coprocessor
fnstsw ss:[bx] ; try to get status word

pop ax ; if low 8 bits are zero,
or al,al ; coprocessor is present

jnz initx ; jump if no coprocessor

fldcw ss:[bx+2] ; load coprocessor control word

initx: pop ax ; restore registers
pop bx
ret ; and return result in Z flag

init87 endp

_TEXT ends

end