lowpassexample_psv.s

dsPIC30F Code ——学习PIC单片机（16位）的好资料

; ..............................................................................
;    File   lowpassexample_psv.s
; ..............................................................................

		.equ lowpassexample_psvNumTaps, 75

; ..............................................................................
; Allocate and initialize filter taps

		.section .lowpassexample_psvconst, "x"
		.align 256

lowpassexample_psvTaps:
.hword 	0xFFFA,	0xFFFB,	0x0000,	0x000B,	0x0017,	0x001E,	0x0017,	0x0000,	0xFFDF
.hword 	0xFFBF,	0xFFB2,	0xFFC7,	0x0000,	0x004F,	0x0095,	0x00AC,	0x007A,	0x0000
.hword 	0xFF61,	0xFEDA,	0xFEB2,	0xFF16,	0x0000,	0x012E,	0x022B,	0x0277,	0x01BD
.hword 	0x0000,	0xFDB7,	0xFBB4,	0xFAF3,	0xFC45,	0x0000,	0x05CF,	0x0CB1,	0x1337
.hword 	0x17E1,	0x1993,	0x17E1,	0x1337,	0x0CB1,	0x05CF,	0x0000,	0xFC45,	0xFAF3
.hword 	0xFBB4,	0xFDB7,	0x0000,	0x01BD,	0x0277,	0x022B,	0x012E,	0x0000,	0xFF16
.hword 	0xFEB2,	0xFEDA,	0xFF61,	0x0000,	0x007A,	0x00AC,	0x0095,	0x004F,	0x0000
.hword 	0xFFC7,	0xFFB2,	0xFFBF,	0xFFDF,	0x0000,	0x0017,	0x001E,	0x0017,	0x000B
.hword 	0x0000,	0xFFFB,	0xFFFA

; ..............................................................................
; Allocate delay line in (uninitialized) Y data space

		.section .ybss,  "b"
		.align 256

lowpassexample_psvDelay:
		.space lowpassexample_psvNumTaps*2

; ..............................................................................
; Allocate and intialize filter structure

		.section .data
		.global _lowpassexample_psvFilter

_lowpassexample_psvFilter:
.hword lowpassexample_psvNumTaps
.hword psvoffset(lowpassexample_psvTaps)
.hword psvoffset(lowpassexample_psvTaps)+lowpassexample_psvNumTaps*2-1
.hword psvpage(lowpassexample_psvTaps)
.hword lowpassexample_psvDelay
.hword lowpassexample_psvDelay+lowpassexample_psvNumTaps*2-1
.hword lowpassexample_psvDelay

; ..............................................................................
; ..............................................................................
; Sample assembly language calling program
;  The following declarations can be cut and pasted as needed into a program
;		.extern	_FIRFilterInit
;		.extern	_BlockFIRFilter
;		.extern	_lowpassexample_psvFilter
;
;		.section	.bss
;
;	 The input and output buffers can be made any desired size
;	   the value 40 is just an example - however, one must ensure
;	   that the output buffer is at least as long as the number of samples
;	   to be filtered (parameter 4)
;input:		.space	40
;output:	.space	40
;		.text
;
;
;  This code can be copied and pasted as needed into a program
;
;
; Set up pointers to access input samples, filter taps, delay line and
; output samples.
;		mov	#_lowpassexample_psvFilter, W0	; Initalize W0 to filter structure
;		call	_FIRFilterInit	; call this function once
;
; The next 4 instructions are required prior to each subroutine call
; to _BlockFIRFilter
;		mov	#_lowpassexample_psvFilter, W0	; Initalize W0 to filter structure
;		mov	#input, W1	; Initalize W1 to input buffer 
;		mov	#output, W2	; Initalize W2 to output buffer
;		mov	#20, W3	; Initialize W3 with number of required output samples
;		call	_BlockFIRFilter	; call as many times as needed