; EECS 452 recursive sine/cosine generator
;
;  6 Oct 2003 .. initial version .. KM
; 12 Oct 2003 .. sine/cosineine version .. KM
;  2 Nov 2003 .. repairs .. KM

        .data 
        
        .bss    w_1,1                        ; delay stage 1 in data memory
        .bss    w_2,1                        ; delay stage 2 in data memory

        .sect ".text"                        ; place into the code section
        .align 4                             ; force 32-bit boundary

        .global _bsinegen                    ; make entry visible to linker

cosine  .set    32488                        ; cosine in Q15
r       .set    (-0x7FFF)                    ; define start w_1 value, Q15
s       .set    0x4000                       ; define start w_2 value, Q15


_bsinegen:
        bset    sxmd                         ; enable sign extend
        bset    frct                         ; shift left 1 on multiply
        bset    m40                          ; use 40 bit accumulator
        bset    rdm                          ; round
        bclr    c54cm                        ; not C54x compatible
        mov     #r,*(#w_1)                   ; initialize w_1
        mov     #s,*(#w_2)                   ; initialize w_2
L1:     
        ; The following section is to be written by students
        
        here be dragons
        
        ; end of student section
        
                                        ; move (scaled) w_2 into T0
        mov     T0,port(#0x3002)        ; McBSP_reg(2, McBSP_DXR2) = w_2; left
        mov     *(#w_1),T0
        mov     T0,port(#0x3003)        ; McBSP_reg(2, McBSP_DXR1) = w_1; right
L2:
        btst    #1,port(#0x3004),tc1 
        bcc     L2,!tc1       ;while((McBSP_reg(2, McBSP_SPCR2)&0x0002) == 0);
        b       L1            ;generate next sinewave value
        
        .end