diir.asm

IIR（无限冲激相应）滤波器的DSP实现

			.title  "diir.asm"
			.mmregs
			.global  start
			.def   start, _c_int00
N			.set   16
	       
table
			.word 63, 0, -188, 0, 188, 0, -63
			.word 0, 11675, 0, 9663, 0, 2948
			.data
INPUT		.copy  "iirin.inc"
INBUF		.usect  "INBUF",256
OUTPUT		.usect  "OUTPUT",256
BN			.usect  "BN",N+1
AN			.usect  "AN",N+1
			.text
			.asg AR0, INDEX_P
			.asg AR2, XN_P
			.asg AR3, ACOEF_P
			.asg AR4, YN_P
			.asg AR5, BCOEF_P
_c_int00
            b start
            nop
            nop
start:		SSBX   FRCT
			SSBX   OVM
			SSBX   SXM
			STM    #BN+N,AR1
			RPT    #N
			MVPD   #table,*AR1-
		    STM    #AN+N-1,AR1
			RPT    #N-1
			MVPD   #table+N+1,*AR1-  
			STM    #OUTPUT, AR1
			RPTZ   A, #255
			STL    A, *AR1+
			STM    #INBUF,AR1
			RPT    #255
			MVPD   #INPUT,*AR1+
			STM    #OUTPUT,YN_P
			STM    #INBUF,XN_P
			STM    #N-1,INDEX_P
			STM    #255,BRC
			RPTB   LOOP-1
IIR:		SUB    A,A
			STM    #BN,BCOEF_P
			STM    #AN,ACOEF_P
			RPT    #N-1
			MAC    *XN_P+,*BCOEF_P+,A
			MAC    *XN_P,*BCOEF_P,A
			MAR    *XN_P-0
			RPT    #N-1
			MAC    *YN_P+,*ACOEF_P+,A
			STH    A,*YN_P-0
LOOP:
EEND		B   EEND
			.end