Category : Files from Magazines
Archive   : ITP9007.ZIP
Filename : TONES.PAS
{ TONES - a set of functions that provide some
interesting sonic effects. Useful for games
or alerts. }
INTERFACE
PROCEDURE Tone(CycleLen,NbrCycles: Integer);
PROCEDURE Noise(D: Longint);
PROCEDURE Chirp(F1,F2,Cycles: Integer);
PROCEDURE Sound2(F: Longint);
PROCEDURE NoSound2;
IMPLEMENTATION
{ Tone - output a tone
INP: cyclen - Length (counts) for 1/2 cycle
numcyc - number of cycles to make }
PROCEDURE Tone(CycleLen,NbrCycles: Integer);
VAR
T,I,J : Integer;
BEGIN
NbrCycles := NbrCycles SHL 1; {# half Cycles}
T := Port[$61]; {Port contents}
FOR I := 1 TO NbrCycles DO
BEGIN
T := T XOR 2;
Port[$61] := T;
FOR J :=1 TO CycleLen DO
END
END;
{ Noise - make noise for a certain amount of
counts.
INP: D - the number of kilocounts of Noise}
PROCEDURE Noise(D: Longint);
VAR
Count : Longint;
T,J,I : Integer;
BEGIN
T := Port[$61];
Count := 0;
WHILE Count < D DO
BEGIN
J := (Random(32768) MOD 128) SHL 4;
FOR I := 1 TO J DO;
T := T XOR 2;
Port[$61] := T;
Inc(Count,J)
END
END;
{ Chirp - create a 'bird Chirp' TYPE Noise
INP:F1 - # OF counts FOR the starting freq.
F2 - # OF counts FOR the ending freq.
Cycles - # OF Cycles OF each frequency }
PROCEDURE Chirp(F1,F2,Cycles: Integer);
VAR
I,J,K,L : Integer;
BEGIN
L := Port[$61];
Cycles := Cycles * 2;
I := F1;
WHILE I <> F2 DO
BEGIN
FOR J := 1 TO Cycles DO
BEGIN
L := L XOR 2;
Port[$61] := L;
FOR K := 1 TO I DO
END;
IF F1 > F2 THEN Dec(I)
ELSE Inc(I)
END
END;
{ Sound2 - Generate a continuous tone using the
internal timer.
INP: F - the desired frequeny }
PROCEDURE Sound2(F: Longint);
VAR
C : Longint;
BEGIN
IF F < 19 THEN F := 19; {Prevent overflow}
C := 1193180 DIV F;
Port[$43] := $B6; {Program new divisor}
Port[$42] := C MOD 256; {Rate into the timer}
Port[$42] := C DIV 256;
C := Port[$61]; {Enable speaker output}
Port[$61] := C OR 3 {from the timer }
END;
{ NoSound2 - turn off the continuous tone }
PROCEDURE NoSound2;
VAR
C : Integer;
BEGIN
C := Port[$61]; {Mask off speaker}
Port[$61] := C AND $FC {output from timer}
END;
END.
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