;LP11SIM.ASM - FIR LOWPASS FILTER WITH 11 COEFF FOR SIMULATION .start ".text",0x809900 ;where text begins .start ".data",0x809C00 ;where data begins .data ;data section IN_ADDR .word INB ;starting address for input OUT_ADDR .word OUTB ;starting address for output XB_ADDR .word XN+LENGTH-1 ;bottom address of circ buffer HN_ADDR .word COEFF ;starting addr of coefficients COEFF .float 0 ;H10 .float 0.0468, 0.1009, 0.1514, 0.1872, 0.2 .float 0.1872, 0.1514, 0.1009, 0.0468 H0 .float 0 ;H0 LENGTH .set H0-COEFF+1 ;# of coefficients INB .float 10000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 OUTB .float 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 .brstart "XN_BUFF",16 ;align samples buffer XN .sect "XN_BUFF" ;section for input samples .loop LENGTH ;buffer size for samples .float 0.0 ;initialize samples to zero .endloop ;end of loop .entry BEGIN ;start of code .text BEGIN LDP @0x809800 ;init to data page 128 LDI LENGTH,BK ;size of circular buffer LDI @XB_ADDR,AR1 ;last sample address ->AR1 LDI @IN_ADDR,AR2 ;input address -->AR2 LDI @OUT_ADDR,AR3 ;output address -->AR3 FILT LDI LENGTH-1,AR4 ;length in AR4 LOOP LDF *AR2++,R3 ;input new sample STF R3,*AR1++% ;store newest sample LDI @HN_ADDR,AR0 ;AR0 points to H(N-1) LDF 0,R0 ;init R0 LDF 0,R2 ;init R2 RPTS LENGTH-1 ;repeat LENGTH-1 times MPYF3 *AR0++,*AR1++%,R0 ;R0 = HN*XN || ADDF3 R0,R2,R2 ;accumulation in R2 DBNZD AR4,LOOP ;delayed branch until AR4<0 ADDF R0,R2 ;last mult result accumulated FIX R2,R7 ;convert float R2 to integer R7 STI R7,*AR3++ ;store into output buffer WAIT BR WAIT ;wait .end ;end