Language/OS - Multiplatform Resource Library

home *** CD-ROM | disk | FTP | other *** search

/ Language/OS - Multiplatform Resource Library / LANGUAGE OS.iso / dsp / dspgroup / fft32010.arc / PROGRAM.4 < prev next >

Wrap

Text File | 1984-11-13 | 7.1 KB | 367 lines

IDT 'FFT4' * * Cooley-Tukey Radix-4, DIF FFT Program * * Single radix-4 butterfly. * Complex input data - size limited only by program memory availability. * Uses table lookup of twiddle factors. * No scaling is done on intermediate values in the program. * External data RAM is addressed via peripheral I/O instructions. * An address counter is required and is loaded by a write * to port 0. Data is read from and written to port 1. * Data in the external RAM assumes complex data with corresponding * real and imaginary data values in consecutive locations. * * N is the size of the transform (N = 4**M). N EQU 64 M EQU 3 * * Data memory allocation. * XI EQU 0 * Data values for butterfly YI EQU 1 XI1 EQU 2 YI1 EQU 3 XI2 EQU 4 YI2 EQU 5 XI3 EQU 6 YI3 EQU 7 I EQU 8 * Data indices I1 EQU 9 I2 EQU 10 I3 EQU 11 CO1 EQU 12 * Twiddle factor coefficients CO2 EQU 13 CO3 EQU 14 SI1 EQU 15 SI2 EQU 16 SI3 EQU 17 N1 EQU 18 * Increment to I N2 EQU 19 * Index separation IA EQU 20 * Index to twiddle factors IE EQU 21 * Increment to IA J EQU 22 * Counters K EQU 23 R1 EQU 24 * Temporaries R2 EQU 25 S1 EQU 26 S2 EQU 27 R3 EQU 28 R4 EQU 29 S3 EQU 30 S4 EQU 31 XJ EQU 32 YJ EQU 33 TEMP EQU 34 HOLDN EQU 35 * Contains the value N QUARTN EQU 36 * Contains the value N/4 ONE EQU 37 * Contains the value 1 TABLE EQU 38 * Location of coefficient table * * Begin program memory section. * AORG 0 START LDPK 0 LACK 1 SACL IE * Initialize IE = 1 SACL ONE LT ONE MPYK SINE PAC SACL TABLE * Save address of coefficient table MPYK N PAC SACL HOLDN SACL N2 * Initialize N2 = N LAC HOLDN,14 SACH QUARTN * QUARTN = N/4 LARK AR0,M-1 * AR0 contains K value KLOOP LARP 1 LAC N2 SACL N1 * N1 = N2 LAC N2,14 SACH N2 * N2 = N2/4 ZAC SACL J SACL IA LAR AR1,N2 * AR1 contains J value MAR *- * Start at N2-1 JLOOP LAC TABLE ADD IA TBLR SI1 * Get twiddle factor 1 ADD QUARTN TBLR CO1 LAC TABLE ADD IA,1 TBLR SI2 * Get twiddle factor 2 ADD QUARTN TBLR CO2 LAC TABLE ADD IA,1 ADD IA TBLR SI3 * Get twiddle factor 3 ADD QUARTN TBLR CO3 LAC IA ADD IE SACL IA * IA = IA + IE LAC J,1 SACL I * I = J (data organized ar real value followed * * by imaginary so address I is 2 times J). ILOOP LAC I ADD N2,1 SACL I1 * I1 = I + N2 ADD N2,1 SACL I2 * I2 = I1 + N2 ADD N2,1 SACL I3 * I3 = I2 + N2 * OUT I,PA0 * Output address of XI IN XI,PA1 * Read real and imaginary parts IN YI,PA1 OUT I1,PA0 * Output address of XI1 IN XI1,PA1 * Read real and imaginary parts IN YI1,PA1 OUT I2,PA0 * Output address of XI2 IN XI2,PA1 * Read real and imaginary parts IN YI2,PA1 OUT I3,PA0 * Output address of XI3 IN XI3,PA1 * Read real and imaginary parts IN YI3,PA1 * * Compute butterfly. * LAC XI ADD XI2 SACL R1 * R1 = X(I) + X(I2) SUB XI2,1 SACL R3 * R3 = X(I) - X(I2) LAC YI ADD YI2 SACL S1 * S1 = Y(I) + Y(I2) SUB YI2,1 SACL S3 * S3 = Y(I) - Y(I2) LAC XI1 ADD XI3 SACL R2 * R2 = X(I1) + X(I3) SUB XI3,1 SACL R4 * R4 = X(I1) - X(I3) LAC YI1 ADD YI3 SACL S2 * S2 = Y(I1) + Y(I3) SUB YI3,1 SACL S4 * S4 = Y(I1) - Y(I3) * LAC R1 ADD R2 SACL XI * X(I) = R1 + R2 SUB R2,1 SACL R2 * R2 = R1 - R2 LAC R3 SUB S4 SACL R1 * R1 = R3 - S4 ADD S4,1 SACL R3 * R3 = R3 + S4 * LAC S1 ADD S2 SACL YI * Y(I) = S1 + S2 SUB S2,1 SACL S2 * S2 = S1 - S2 LAC S3 ADD R4 SACL S1 * S1 = S3 + R4 SUB R4,1 SACL S3 * S3 = S3 - R4 * LT CO1 MPY S3 PAC LT SI1 MPY R3 SPAC SACH YI1,1 * Y(I1) = CO1*S3 - SI1*R3 MPY S3 PAC LT CO1 MPY R3 LTA CO2 SACH XI1,1 * X(I1) = CO1*R3 + SI1*S3 MPY S2 PAC LT SI2 MPY R2 SPAC SACH YI2,1 * Y(I2) = CO2*S2 - SI2*R2 MPY S2 PAC LT CO2 MPY R2 LTA CO3 SACH XI2,1 * X(I2) = CO2*R2 + SI2*S2 MPY S1 PAC LT SI3 MPY R1 SPAC SACH YI3,1 * Y(I3) = CO3*S1 - SI3*R1 MPY S1 PAC LT CO3 MPY R1 APAC SACH XI3,1 * X(I3) = CO3*R1 + SI3*S1 * * Output results of the butterfly. * OUT I,PA0 OUT XI,PA1 OUT YI,PA1 OUT I1,PA0 OUT XI1,PA1 OUT YI1,PA1 OUT I2,PA0 OUT XI2,PA1 OUT YI2,PA1 OUT I3,PA0 OUT XI3,PA1 OUT YI3,PA1 * * Add increment for next loop. * LAC I ADD N1,1 SACL I * I = I + N1 SUB HOLDN,1 BLZ ILOOP LAC J ADD ONE SACL J * J = J + 1 BANZ JLOOP LAC IE,2 SACL IE * IE = IE*4 LARP 0 BANZ KLOOP * * Digit reverse counter for radix-4 FFT computation. * DRC4 ZAC SACL J SACL I LARP 0 LAR AR0,HOLDN MAR *- MAR *- DRLOOP SUB J BGEZ NOSWAP * * Swap I and J locations. * OUT I,PA0 IN XI,PA1 IN YI,PA1 OUT J,PA0 IN XJ,PA1 IN YJ,PA1 OUT J,PA0 OUT XI,PA1 OUT YI,PA1 OUT I,PA0 OUT XJ,PA1 OUT YJ,PA1 NOSWAP LAC QUARTN,1 SACL K INLOOP LT K MPYK 3 PAC SACL TEMP SUB J BGZ OUTL LAC J SUB TEMP SACL J LAC K,14 SACH K B INLOOP OUTL LAC J ADD K SACL J LAC I ADD ONE,1 SACL I BANZ DRLOOP * * End of FFT. * STOP B STOP * * Sine and cosine tables for coefficients. * SINE EQU $ DATA 0 DATA 3211 DATA 6392 DATA 9511 DATA 12539 DATA 15446 DATA 18204 DATA 20787 DATA 23169 DATA 25329 DATA 27244 DATA 28897 DATA 30272 DATA 31356 DATA 32137 DATA 32609 COSINE EQU $ DATA 32767 DATA 32609 DATA 32137 DATA 31356 DATA 30272 DATA 28897 DATA 27244 DATA 25329 DATA 23169 DATA 20787 DATA 18204 DATA 15446 DATA 12539 DATA 9511 DATA 6392 DATA 3211 DATA 0 DATA -3211 DATA -6392 DATA -9511 DATA -12539 DATA -15446 DATA -18204 DATA -20787 DATA -23169 DATA -25329 DATA -27244 DATA -28897 DATA -30272 DATA -31356 DATA -32137 DATA -32609 DATA -32767 DATA -32609 DATA -32137 DATA -31356 DATA -30272 DATA -28897 DATA -27244 DATA -25329 DATA -23169 DATA -20787 DATA -18204 DATA -15446 DATA -12539 DATA -9511 DATA -6392 DATA -3211 END