Method and apparatus for emulating a frequency modulation device

A method of emulating a frequency modulation sound chip comprising:

• providing a frequency modulation emulator in communication with a computer system, the frequency modulation emulator providing an emulator addressable memory space substantially similar to an emulated addressable memory space on the emulated frequency modulation sound chip, the frequency modulation emulator being suitable for communication with a frequency modulation application implemented on the computer system, wherein the emulator receives audio data through the addressable memory space from the frequency modulation application, the audio data including timer data, mode data, key.sub.-- on data and rhythm data, the frequency modulation emulator including,
• a decoder in communication with the computer system, the decoder providing the addressable memory space capable of receiving the audio data from the frequency modulation application,
• a memory in communication with the decoder and a frequency modulation generator, wherein the memory receives the audio data from the decoder and the memory provides the frequency modulation generator with access to the audio data,
• a variable length timer in communication with the decoder, the timer receiving the timer data from the frequency modulation application by way of the decoder, wherein the timer data determines the length of the variable length timer,
• a status register in communication with the variable length timer and the frequency modulation application, the status register including,
• a timer flag, the variable length timer setting the timer flag when the timer has overflowed, and
• a version bit, the status register being masked in the addressable memory space such that the frequency modulation application can access the timer flag and the version bit from the status register through the addressable memory space, wherein the status register is in communication with the frequency modulation generator such that the frequency modulation generator is capable of setting the timer flag and the version bit,
• a mode register in communication with the decoder and the frequency modulation generator, the mode register receiving the mode data from the frequency modulation application by way of the decoder, wherein the frequency modulation generator is capable of accessing the mode data from the mode register,
• a key decoder in communication with the decoder, the key decoder receiving the key.sub.-- on data from the decoder, and
• a key register in communication with the key decoder and the frequency modulation generator, the key register including a melodic transition flag and a rhythmic transition flag, wherein the key decoder sets the melodic transition flag when the key.sub.-- on data transitions from a first key state to a second key state and back to the first key state within a first predetermined interval of time, and the key decoder sets the rhythmic transition flag when the rhythm data transitions from a first rhythm state to a second rhythm state and back to the first rhythm state within the first predetermined interval of time, and the frequency modulation generator is capable of accessing the melodic and rhythmic transition flags;
• and
• implementing the frequency modulation generator on the computer system, the frequency modulation generator accessing the audio data front, the frequency modulation emulator and processing the audio data to produce an audio signal, implementing the frequency modulation generator including,
• initializing the frequency modulation generator chip including,
• initializing the memory, such that the memory is in a state substantially similar to a start up state of the emulated frequency modulation chip,
• initializing the timer to a predetermined state,
• initializing the timer flag and the version bit of the status register,
• initializing the mode register to a predetermined state,
• initializing the key register to a predetermined state,
• retrieving the mode data from the mode register, the frequency modulation generator operating in a one of a plurality of emulation modes based upon the value of the mode data,
• repeatedly retrieving the audio data from the memory and the melodic and rhythmic transition bits from the status register at the first predetermined interval of time,
• generating the audio signal described by the audio data and the melodic and rhythmic transition flags, the audio signal including a plurality of voices, and
• resetting the melodic and rhythmic transition flags if the melodic and rhythmic transition flags were set, respectively.

A method of emulating a frequency modulation sound chip comprising:

• receiving an instruction from a frequency modulation application implemented on a computer system to play an audio signal, the instruction including audio data describing the audio signal to be played, receiving the instruction being performed by a frequency modulation emulator;
• storing the instruction in a memory of the frequency modulation emulator;
• retrieving the instruction from the memory, retrieving the instruction being implemented by a frequency modulation generator implemented on the computer system;
• and
• generating the audio signal described by the first plurality of data, generating the audio signal being implemented by the frequency modulation generator.

A frequency modulation generator for use with a frequency modulation emulator, the frequency modulation generator implemented on a computer system for emulating a frequency modulation sound chip, the frequency modulation generator arranged to configure the computer system to:

• retrieve audio data from the frequency modulation emulator;
• and
• generate an audio signal, the audio signal being described by the audio data wherein the audio data includes a key on data and a rhythmic data;
• repeatedly retrieve the audio data from the frequency modulation generator chip at a predetermined interval of time;
• retrieve a melodic transition flag generated by the frequency modulation emulator along with the audio data, the melodic transition flag being set when the key on data transitions from a first key on state to a second key.sub.-- on state and back to the first key.sub.-- on state within the predetermined interval of time;
• and
• retrieve a rhythmic transition flag generated by the frequency modulation emulator along with the audio data, the rhythmic transition flag being set when the rhythm data transitions from a first rhythmic state to a second rhythmic state and back to the first rhythmic state within the predetermined interval of time;
• such that the generation of the audio signal incorporates the key.sub.-- on data, and the melodic and rhythmic flags.

A frequency modulation sound card for use with a frequency modulation generator, the frequency modulation generator being implemented on a computer system, the frequency modulation sound card comprising:

• a decoder in communication with a computer system, the decoder providing an addressable memory space substantially similar to an emulated frequency modulation sound chip and capable of receiving audio data from a frequency modulation application implemented on the computer system;
• and
• a memory in communication with the decoder and the frequency modulation generator, wherein the memory receives the audio data from the decoder and the memory allows access to the audio data to the frequency modulation generator;
• wherein frequency modulation generator is arranged to configure the computer system to retrieve audio data from the memory and generate an audio signal, the audio signal being described by the audio data.