C	-+-+-+-+-+   H A E P R P . F T   -+-+-+-+-+
C
C	PREP FOR THE FFT
C
	SUBROUTINE PRPFFT
	INCLUDE HAEBUF.FI
	INCLUDE HAEGSA.FI
	INCLUDE HAEPTI.FI
	INCLUDE HAETTY.FI
	INCLUDE HABRK.FI
C
	INTEGER LOG2
	EXTERNAL LOG2
C
	INTEGER I,J,K,DA(3),BAND,LIMIT	@ DO LOOP COUNTERS & LIMITS
     	REAL TEMP,CPUTIM
C
C
10	CONTINUE
C
C	HERE WE TEST FOR CORRECT FREQUENCY LIMITS OF THE EEG BAND (1-5)
	DO 12 BAND=1,5
	DO 12 LIMIT=1,2
	IF (FREQU(BAND,LIMIT).LE.SAMRAT/2) GOTO 12
	WRITE (TTO,101) BAND,SAMRAT
	FREQU(BAND,LIMIT)=COND(LIMIT.EQ.1,SAMRAT/2.-.1,SAMRAT/2.)
12	CONTINUE
C
	IF (OPTION.NE.12 .OR. ENDS.LT.SPAN) CALL ASKHIM(4) @ CO* DOESN'T ASK SCILLY QUESTIONS IF THERE ARE CORRECT PARAMETERS
C
C	TEST FOR VALID INPUT PARAMETERS
C
	IF BREAK(11) RETURN		@ USER GETS RID OF PROGRAM
	INCR=SAMRAT*SPAN		@ NUMBER OF POINTS FOR EACH FFT --> INCR
	IF (INCR.LE.2048) GOTO 22	@ MORE THAN 2048 POINTS TO SCAN?
	WRITE (TTO,6) SPAN		@ TOO LESS MEMORY
	GOTO 10
22	CONTINUE
	IF (SPAN.LE.ENDS) GOTO 23	@ LESS THAN ONE PASS?
	WRITE (TTO,8) SPAN,ENDS
	GOTO 10
23	CONTINUE
	IF (ENDS.LE.SAMCNT/SAMRAT) GOTO 24 @ IF THE END DOES NOT EXCEED THE SAMPLE COUNT THEN WE GO 24 ELSE
	I=SAMCNT/SAMRAT			@ WE COMPUTE THE SAMPLING TIME IN SECONDS
	WRITE (TTO,2) ENDS,I		@  IN ORDER TO PRINT AN DIAGNOSTIC MSG
	ENDS=SAMCNT/SAMRAT		@  AND THE WE BUMP THE SAMPLING TIME INTO ENDS
24	CONTINUE
	EXPON=LOG2(INCR)		@ TEST FOR POWER OF 2
	IF (EXPON.GT.0) GOTO 20		@ IF INCR IS A POWER OF TWO THEN GOTO 20
	WRITE (TTO,3) SAMRAT,SPAN	@ NO POWER OF TWO
	GOTO 10				@ READ NEXT VALUE
20	TEMP=AMOD(FLOAT(ENDS-BEGIN),FLOAT(SPAN)) @ COMPUTE SECONDS TO TRANSFORM
	IF (TEMP.LT.0.1) GOTO 30	@ ARE THERE SOME SECONDS LEFT?
	TEMP=AMOD(FLOAT(SAMCNT)/FLOAT(SAMRAT),FLOAT(SPAN))
	WRITE (TTO,4) TEMP		@ TELL THE USER THERE IS SOMETHING REMAINING
30	ENDS=BEGIN+(ENDS-BEGIN)/SPAN*SPAN @ COMPUTE THE END OF THE SPECTRUM TO SCAN
C
	I=NCOND(OVRLAP,2*(ENDS-BEGIN)/SPAN,(ENDS-BEGIN)/SPAN) @ IF THE INTERMEDIATE RESULTS FIT ONTO UNIT 5 THEN
	I=I/4				@ FOUR DATA WORDS PER RECORD
	I=I+STSCAN			@ COMPUTE NUMBER OF RECORDS NESESCARY
	IF (MAXBL5.GE.I) GOTO 40	@  RETURN ELSE PRINT AN ERROR MSG
	WRITE (TTO,9) I
	OPTION=0			@ PREVENT LOOPING IF CO*
	GOTO 10
C
C
40	FREQU(1,2)=AMIN1(SAMRAT/2.,FREQU(1,2)) @ HIGHEST FREQUENCY OF THE INPUT SIGNAL --> UPPER LIMIT OF THE FIRST BAND
	IF BREAK(11) RETURN
	CALL ADATE(DA)			@ ASK FRTS FOR THE CURRENT DATE AND INSERT IT INTO THE HEADER
	WRITE (3,1) SETNUM,CHANEL,LABEL,DA
	WRITE (3,100) ((FREQU(I,J),J=1,2),I=1,5)
	RETURN
C
C
1	FORMAT ('1SATZ:',I3,' KANAL',I2,' :',10A6,2(A2,1H/),A2)
100	FORMAT (1H0,15X,5(F6.1,'  -',F6.1,5X))
101	FORMAT (' FUER EEG BAND',I2,' REICHT DIE MESSRATE VON',I4,
     *  ' HZ NICHT AUS. BANDGRENZE VERRINGERT.')
2	FORMAT (' RECHNUNG SOLL MIT',I5,' SEC UEBER DAS DATENENDE',
     *   I5,' SEC HINAUSGEHEN.')
3	FORMAT (' DAS PRODUKT AUS MESSRATE',I3,' [HZ] UND SPANNE',
     *  I3,' [SEK] IST KEINE ZWEIERPOTENZ.')
4	FORMAT (' AM ENDE DES SPEKTRUMS BLEIBEN',F4.1,' SEKUNDEN',
     *  ' UNBERUECKSICHTIGT.')
6	FORMAT (' MEHR ALS 2048 PUNKTE FUER EINE FFT:',I7)
8	FORMAT (' SPANNE MIT',I3,' SEK. GROESSER ALS DIE MESSZEIT',I3
     *  ,' SEKUNDEN.')
9	FORMAT (' FILE 5 FUER DIE ZWISCHENWERTE ZU KLEIN:',I5,
     *  ' SPANNE VERGROESSERN.')
	END
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