iir1.asm

这里面有很多dsp应用程序源码

*************************************
*用单操作数指令实现二阶IIR滤波器    *
*反馈通道:x0=w(n)=x(n)+A1*x1+A2*x2  *
*前向通道:y(n)=B0*x0+B1*x1+B2*x2    *
*************************************
	.title	"IIR1.asm"
	.mmregs
	.def	start
x0	.usect	"x",1
x1	.usect	"x",1
x2	.usect	"x",1
B2	.usect	"COEF",1
B1	.usect	"COEF",1
B0	.usect	"COEF",1	
A2	.usect	"COEF",1
A1	.usect	"COEF",1
PA0	.set	0
PA1	.set	1
	.data
table	.word	0		;x(n-1)
	.word	0		;x(n-2)
	.word	1*32768/10	;B2=0.1
	.word	2*32768/10	;B1=0.2
	.word	3*32768/10	;B0=0.3
	.word	5*32768/10	;A2=0.5
	.word	-4*32768/10	;A1=-0.4
	.text
start:	LD	#x0,DP
	SSBX	FRCT
	STM	#x1,AR1		;传送初始化数据x(n-1),x(n-2)
	RPT	#1
	MVPD	#table,*AR1+
	STM	#B2,AR1		;传送系数B2,B1,B0,A2,A1
	RPT	#4
	MVPD	#table+2,*AR1+
IIR1:	PORTR	PA1,@x0		;输入数据x(n)
	LD	@x0,16,A	;计算反馈通道,A=x0	
	LD	@x1,T 		;T=x1
	MAC	@A1,A		;A=A+T*A1
	LD	@x2,T		;T=A2
	MAC	@A2,A		;A=A+T*A2
	
	STH	A,@x0
	
	MPY	@B2,A		;计算前向通道
	
	LTD	@x1
	MAC	@B1,A

	LTD	@x0
	MAC	@B0,A
	
	STH	A,@x0		;暂存y(n)
	BD	IIR1		;循环
	PORTW	@x0,PA0		;输出结果y(n)
	.end