of Microprocessors

664 MUSICAL ApPLICATIONS OF MICROPROCESSORS
0222 1l0A ; WAVEFORM TABLE FILL USING FOURIER SERIES
0223 1l0A
0224 1l0A *~ $80 STORAGE IN PAGE ZERO
0225 0080 HRMACC *=*+ 2 HARMONIC ACCUMULATOR
0226 0082 PNTNO *=*+ 1 POINT NUMBER WITHIN CYCLE OF WAVE
0227 0083 NDXACC *=*+ 1 INDEXING ACCUMULATOR
0228 0084 HRMCNT *=*+ 1 HARMONIC COUNTER
0229 0085 MAX *=*+ 1 MAXIMUM WAVEFORM AMPLITUDE
0230 0086 WAVETB *=*+ 2 ADDRESS OF WAVEFORM TABLE TO FILL
0231 0088
0232 0088 NHARM *=*+ 1 HIGHEST HARMONIC TO GENERATE (16 MAX)
0233 0089 FSRAM *=*+ 32" ROOM FOR 16 HARMONIC AMPLITUDES AND
0234 00A9 PHASES
0235 00A9
0236 00A9 *~ $2000 PROGRAM ORIGIN
0237 2000
0238 2000 WAVEFORM TABLE FILL ROUTINE
0239 2000 THIS SUBROUTINE FILLS THE WAVEFORM TABLE AT WAVETB WITH 256
0240 2000 SAMPLES OF THE WAVEFORM SPECIFIED BY THE SPECTRUM AT FSRAM.
0241 2000 MAX MUST HAVE BEEN PREVIOUSLY SET GREATER THAN TWICE THE
0242 2000 ABSOLUTE VALUE OF THE LARGEST SAMPLE THAT WILL BE ENCOUNTERED.
0243 2000
0244 2000 A900 FILL LOA #0 ZERO THE POINT NUMBER
0245 2002 8582 STA PNTNO
0246 2004 204020 FILL! JSR FSEVAL EVALUATE A WAVEFORM POINT
0247 2007 A580 LOA HRMACC DIVIDE POINT BY MAXIMUM POINT FOR SCALING
0248 2009 85BO STA ACCH FIRST TRANSFER POINT TO PSEUDO
0249 200B A581 LOA HRMACC+1 ACCUMULATOR FOR USE AS THE DIVIDEND
0250 2000 85Bl STA ACCL
0251 200F A585 LOA MAX LOAD MAX AS THE DIVISOR (UNSIGNED)
0252 2011 20C710 JSR DIV2Q DO A TWO QUADRANT DIVIDE
0253 2014 A5B1 LOA ACCL GET THE SIGNED QUOTIENT
0254 2016 A482 LOY PNTNO GET THE POINT NUMBER
0255 2018 9186 STA (WAVETB). Y STORE RESULT IN WAVEFORM TABLE
0256 20IA E682 INC PNTNO INCREMENT THE POINT NUMBER
0257 20IC DOE6 BNE FILL! GO FOR ANOTHER POINT IF NOT FINISHED
0258 201E 60 RTS RETURN WHEN FINISHED
0259 201F
0260 201F SCALE FACTOR DETERMINATION SUBROUTINE
0261 201F THIS SUBROUTINE GOES THROUGH ONE CYCLE OF THE WAVEFORM DEFINED
0262 201F BY THE SPECTRUM AT FSRAM AND FINDS THE POINT WITH THE MAXIMUM
0263 201F MAGNITUDE.
0264 201F THIS MAGNITUDE IS THEN DOUBLED AND INCREMENTED BY ONE AND
0265 201F STORED AS AN UNSIGNED NUMBER.
0266 201F
0267 201F A900 SCALE LOA #0 ZERO THE POINT NUMBER
0268 2021 8582 STA PNTNO
0269 2023 8585 STA MAX ZERO THE MAXIMUM MAGNITUDE
0270 2025 204020 SCALEl JSR FSEVAL EVALUATE A WAVEFORM POINT
0271 2028 A58D LOA HRMACC GET UPPER BYTE OF THE POINT
on 2 202A 1005 BPL SCALE2 SKIP IF POSITIVE
0273 202C 49FF EOR #$FF NEGATE IF NEGATIVE
0274 202E 18 CLC
0275 202F 6901 ADC #1
0276 2031 C585 SCALE2 CMP MAX COMPARE WITH CURRENT MAXIMUM
0277 2033 3002 8MI SCALE3 SKIP IF NOT GREATER
0278 2035 8585 STA MAX UPDATE MAXIMUM IF GREATER
0279 2037 E682 SCALE3 INC PNTNO INCREMENT POINT NUM8ER
0280 2039 DOEA BNE SCALEI GO FOR NEXT POINT IF NOT DONE
0281 203B 0685 ASL MAX DOUBLE AND THEN INCREMENT MAXIMUM VALUE
0282 2030 E685 INC MAX TO AVOID POSSIBLE DIVISON OVERFLOW
0283 203F 60 RTS AND RETURN
0284 2040
0285 2040 FOURIER SERIES POINT EVALUATOR
0286 2040 THIS SUBROUTINE EVALUATES A POINT ON THE WAVEFORM SPECIFIED BY
0287 2040 THE SPECTRUM AT FSRAM.
0288 2040 NHARM SPECIFIES THE HIGHEST HARMONIC TO BE INCLUDED