; v:\ece420\54x\dspclib\c_fft_given_iirc.asm
; mdk - 9/2004    removed window and added coef, state, scale for IIR
; dgs - 9/14/2001
; Use governed by the Creative Commons Attribution License

	.copy "v:\ece420\54x\dspclib\core.inc"

	.global	_bit_rev_data
	.global _fft_data
	.global _coef
	.global _state
	.global _scale

	.global _bit_rev_fft

N               .set 1024
K_FFT_SIZE      .set N
K_LOGN          .set 10

	.sect	".data"
        .align 1024
sine    .copy "v:\ece420\54x\dsplib\twiddle1"
        .align 1024
cosine  .copy "v:\ece420\54x\dsplib\twiddle2"

	.align 4*N
_bit_rev_data .space 16*2*N	; Input to _bit_rev_fft

	.align	4*N
_fft_data .space 16*2*N		; FFT output buffer

; IIR filter
	.align 4	
_coef
	.word  0 
	.word  0
	.word  0
	.word  -13421; -21498
_state
	.space  16*4 
_scale
	.word   19345;  11268

	.sect ".text"

_bit_rev_fft
	ENTER_ASM

	call bit_rev                    ; Do the bit-reversal.

	call fft		        ; Do the FFT

	LEAVE_ASM
        RET                                     

bit_rev
        stm #_bit_rev_data, AR3 ; ar3 -> org. input
        stm #_fft_data, AR7 ; ar7 -> data proc. buf
        MVMM AR7, AR2   ; ar2 -> b_r_d
        stm #K_FFT_SIZE-1, BRC
        rptbd bit_rev_end-1
        stm #K_FFT_SIZE, AR0    ;AR0 = 1/2 size of circ buffer
        mvdd *AR3+, *AR2+
        mvdd *AR3-, *AR2+
        MAR *AR3+0B
bit_rev_end:
        nop
        ret

; Copy the actual FFT subroutine.
fft_data  .set	_fft_data	; FFT code needs this.
          .copy 	"v:\ece420\54x\dsplib\fft.asm"


; If you need any more assembly subroutines, make sure you name them
; _name, and include a ".global _name" directive at the top. Also,
; don't forget to use ENTER_ASM at the beginning, and LEAVE_ASM
; and RET at the end!