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"  ;<-Syntax supported in MPLAB C30
                                                ;v1.20 and before
                .section .lowpassexample_psvconst, code ;<-Syntax supported in MPLAB C30
                                                ;v1.30 and later
                .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"            ;<-Syntax supported in MPLAB C30
                                                ;v1.20 and before
                .section .ydata, data, ymemory  ;<-Syntax supported in MPLAB C30
                                                ;v1.30 and later
                .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