基于DSP开发平台《TI DSP在音频处理中的应用》程序代码

				
				; Example 5 - 3. FIR Filter Based on MAC Instruction for the TMS320C54x DSP
				
				; TEXAS INSTRUMENTS INCORPORATED
					.mmregs
					.include ”main.inc”
				
				
				; the 16 tap FIR coefficients
				
				COFF_FIR_START 	.sect ”coff_fir” ; filter coefficients
						.word 6Fh
						.word 0F3h
						.word 269h
						.word 50Dh
						.word 8A9h
						.word 0C99h
						.word 0FF8h
						.word 11EBh
						.word 11EBh
						.word 0FF8h
						.word 0C99h
						.word 8A9h
						.word 50Dh
						.word 269h
						.word 0F3h
						.word 6Fh
				COFF_FIR_END
				
				FIR_DP 		.usect ”fir_vars”,0
				d_filin 	.usect ”fir_vars”,1
				d_filout 	.usect ”fir_vars”,1
				fir_coff_table 	.usect ”fir_coff”,20
				d_data_buffer 	.usect ”fir_bfr”,40 ; buffer size for the filter
				
					.def fir_init 		; initialize FIR filter
					.def fir_task 		; perform FIR filtering
				;––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
				; Functional Description
				; This routine initializes circular buffers both for data and coeffs.
				;–––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
				
					.asg AR0, FIR_INDEX_P
					.asg AR4,FIR_DATA_P
					.asg AR5,FIR_COFF_P
				
					.sect ”fir_prog”
				
				fir_init:
					STM #fir_coff_table,FIR_COFF_P
					RPT #K_FIR_BFFR–1 			; move FIR coeffs from program
					MVPD #COFF_FIR_START,*FIR_COFF_P+ 	; to data
					STM #K_FIR_INDEX,FIR_INDEX_P
					STM #d_data_buffer,FIR_DATA_P 		; load cir_bfr address for the
										; recent samples
					RPTZ A,#K_FIR_BFFR
					STL A,*FIR_DATA_P+ ; reset the buffer
					STM #(d_data_buffer+K_FIR_BFFR–1), FIR_DATA_P
					RETD
					STM #fir_coff_table, FIR_COFF_P
				
				;––––––––––––––––––––––––––––––––––––––––––––––––––––
				; Functional Description
				;;
				This subroutine performs FIR filtering using MAC instruction.
				; accumulator A (filter output) = h(n)*x(n–i) for i = 0,1...15
				;––––––––––––––––––––––––––––––––––––––––––––––––––
				
					.asg AR6,INBUF_P
					.asg AR7,OUTBUF_P
					.asg AR4,FIR_DATA_P
					.asg AR5,FIR_COFF_P
					
					.sect ”fir_prog”
				
				fir_task:
				; LD #FIR_DP,DP
					STM #K_FRAME_SIZE–1,BRC 	; Repeat 256 times
					RPTBD fir_filter_loop–1
					STM #K_FIR_BFFR,BK 		; FIR circular bffr size
					LD *INBUF_P+, A 		; load the input value
				fir_filter:
					STL A,*FIR_DATA_P+% 		; replace oldest sample with newest
									; sample
					RPTZ A,(K_FIR_BFFR–1)
					MAC *FIR_DATA_P+0%,*FIR_COFF_P+0%,A 		; filtering
					STH A, *OUTBUF_P+ 				; replace the oldest bffr value
				fir_filter_loop
					
				RET