;;; Tremolo Effect 

;;; By:	 Daniel Bertrand

;;; Oct 29, 2000

	include "emu_constants.asm"

	name "tremolo"

in	IO

out	equ	in

;;; sinewave generator:

delta control 10e-4,0,1e-2 ; controls frequency (2*pi*freq/48000)

cosx sta #0.5		 

sinx sta 0		

depth control &0.001,0,&0.001

tmp  dyn	

delay	delay	&0.01

wrt	twrite	delay,0

rd	tread	delay,0	

rd2	tread	delay,0

c1000	sta	$1000

	macs	wrt,in,C_0,C_0

;;; sinwave generator:	

	macs  sinx,sinx,delta,cosx       

	macs1 cosx,cosx,delta,sinx 

;;; calulate address = depth*sin(wt)+0.5*depth

	macs tmp,c1000,depth,C_2^30

	macs tmp,tmp,sinx,depth

	acc3 rd.a,tmp,C_0,wrt.a	

	macints rd2.a,rd.a,C_8,C_256  ;;;next address 

;;; get fractional address:	

	macints tmp,C_0,rd.a,C_LSshift

;;; linear interpolate fraction between the 2 reads

;;; output result	

	interp  out,rd,tmp,rd2

	end