Audio functional unit and system and method for configuring the same

• US 5,689,534 A
• Filed: 10/18/1993
• Issued: 11/18/1997
• Est. Priority Date: 05/12/1992
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Wilson, David F., Oxford, William V., Anderson, Eric C.
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): LUTHER, WILLIAM A
• Application Number:
  US08/138,753
• Time in Patent Office: 1,492 Days
• Field of Search: 377/20, 377/39, 377/47, 375/354, 375/362, 375/225, 375/257, 375/368, 375/355, 375/360, 375/364, 375/371, 375/374, 381/2, 381/77, 364/724.1, 370/84, 370/102, 370/110.1, 370/110.4, 370/111, 370/100.1, 370/85.11, 370/101, 370/105.5, 370/503, 370/516, 370/518, 370/520, 395/200.19, 395/551, 395/555, 395/556, 395/559
• US Class Current: 375/364
• CPC Class Codes: H04H 60/04 Studio equipment; Interconnection of studios
• CPC Class Codes: H04L 7/0331 with a digital phase-locked loop [PLL] processing binary samples, e.g. add/subtract logic for correction of receiver clock H04L7/0337 takes precedence

Abstract

The audio system having a master clock, a serial port clocked according to a serial clock from the audio system, a programmable audio functional circuitry programmable and operable at a plurality of sample rates, and a rate selection control logic which sense a ratio between the serial clock and the master clock. The serial clock is derived from the master clock. The rate selection control logic reprograms the audio functional circuitry based on the ratio, to operate at one of the plurality of sample rates in response to a change in the clock rate of the serial clock, such that the audio functional circuitry operates at another of the plurality of sample rates.

Claims

1. A method for configuring an audio functional unit having a serial port, wherein said audio functional unit is coupled to a master clock and a serial clock, wherein said audio functional unit includes audio functional circuitry that performs a plurality of functions and is operable at a plurality of sample rates, and further wherein the serial clock is derived from the master clock, said method comprising the steps of:

changing the serial clock from an initial clock rate to a desired clock rate;

receiving the master clock and the serial clock internally within said audio functional unit;

determining the ratio of the master clock to the serial clock in response to receiving the master clock and the serial clock, wherein the ratio is indicative of one of the plurality of sample rates;

programming said audio functional circuitry within said audio functional unit according to said ratio, wherein the step of programming comprises setting the sample rate of the audio functional unit based on the ratio, such that said audio functional circuitry is reprogrammed to operate using said one of the plurality of sample rates by changing the serial clock to the desired clock rate of the serial port.

2. The method defined in claim 1 wherein the step of determining includes incrementing a value in response to each of a plurality of master clock pulses of the master clock;

and outputting the value in response to each clock pulse of said serial clock, wherein the plurality of functions are programmed in response to the value.

3. The method defined in claim 2 wherein said audio functional unit includes at least one filter, and said step of programming includes modifying said at least one filter to vary the sample rate.

4. The method defined in claim 2 further including the step of resetting the value after the step of outputting.

5. The method defined in claim 2 wherein the value is output in response to an edge of said clock pulse of said serial clock.

6. The method defined in claim 2 wherein the step of programming includes comparing the value with a previously received value and leaving the sample rate unchanged if the value and the previously received value are the same.

7. The method defined in claim 1 further comprising adjusting the ratio to produce a desired sample rate, wherein said audio functional circuitry is programmed to operate at the desired sample rate.

24. The method defined in claim 1, further comprising the step of transferring signals between the audio functional unit and the serial port utilizing a set of wires, the steps of transferring signals comprising the steps of:

transferring combined audio and command date from the serial port to the audio functional unit through a first conductor;

transferring combined audio and status data from the audio functional unit to the serial port through a second conductor;

transferring the serial clock through a third conductor; and

transferring a synchronization signal through a fourth conductor.

25. The method defined in claim 24 wherein the set of wires comprises only four conductors.

26. The method defined in claim 1 wherein the audio functional unit and the serial port are coupled via a set of wires comprising only four conductors.

27. The method defined in claim 26 further comprising the step of transferring signals between the audio functional unit and the serial port utilizing the set of wires, the steps of transferring signals comprising the steps of:

transferring combined audio and command date from the serial port to the audio functional unit through a first conductor;

transferring combined audio and status data from the audio functional unit to the serial port through a second conductor;

transferring the serial clock through a third conductor; and

transferring a synchronization signal through a fourth conductor.

8. An audio functional unit in an audio system, wherein the audio system includes a master clock, said audio functional unit comprising:

a serial port clocked according to a serial clock from the audio system, wherein the serial clock is at a clock rate and is derived from the master clock;

an audio functional circuitry coupled to the serial port, wherein the audio functional circuitry is programmable, provides a plurality of functions and is operable at a plurality of sample rates; and

rate selection control logic coupled to the audio functional circuitry and coupled to receive the serial clock and the master clock, wherein the rate selection control logic senses a ratio between the serial clock and the master clock and reprograms the audio functional circuitry to operate at one of the plurality of sample rates in response to a change in the clock rate of the serial clock, such that the audio functional circuitry operates at another of the plurality of sample rates.

9. The audio functional unit defined in claim 8 wherein the rate selection control logic comprises:

receiving means for receiving the master clock and the serial clock;

counter means coupled to the receiving means for incrementing a counter value in response to the master clock;

ratio latch means coupled to the counter means and the receiving means for receiving the counter value in response to the serial clock, wherein the counter value comprises an indication of the ratio of the master clock to the serial clock.

10. The audio functional unit defined in claim 9 further comprising initializing means for initializing the counter value to an initial value.

11. The audio functional unit defined in claim 10 where the initializing means includes a register.

12. The audio functional unit defined in claim 8 wherein the rate selection control logic comprises:

a receiver for receiving the master clock and the serial clock;

a counter coupled to the receiver, wherein the counter increments a counter value in response to the master clock;

a ratio latch coupled to the counter and the receiver for receiving the counter value in response to the serial clock, wherein the counter value comprises an indication of the ratio of the master clock to the serial clock.

13. The apparatus defined in claim 12 further comprising a controller coupled to the ratio latch and the counter, wherein the controller controls the loading of the ratio latch and the counter to cause the ratio latch to receive the counter value and the counter to receive an initial value, such that the counter value is loaded into the ratio latch prior to the initial value being loaded into the counter.

14. The apparatus defined in claim 8 wherein the rate control selection logic programs the audio functional circuitry by modifying decimation filters within the audio functional unit.

28. The audio functional unit defined in claim 8 further comprising a set of wires coupling the audio functional circuitry to the serial port, the set of wires comprising:

a first conductor transferring combined audio and command date from the serial I/O interface to the audio functional unit;

a second conductor transferring combined audio and status data from the audio functional unit to the serial I/O interface;

a third conductor transferring the serial clock; and

a fourth conductor transferring a synchronization signal.

29. The method defined in claim 28 wherein the set of wires comprises only four conductors.

30. The method defined in claim 8 wherein the audio functional circuitry and the serial port are coupled via a set of wires comprising only four conductors.

31. The audio functional unit defined in claim 30, the four conductors comprising:

a first conductor transferring combined audio and command date from the serial I/O interface to the audio functional unit;

a second conductor transferring combined audio and status data from the audio functional unit to the serial I/O interface;

a third conductor transferring the serial clock; and

a fourth conductor transferring a synchronization signal.

15. An audio subsystem for use in a system having a master clock, said audio subsystem comprising:

a serial input/output (I/O) interface that transfers information using a serial protocol according to a serial clock generated and modifiable by the serial I/O interface; and

an audio functional unit coupled to the serial I/O interface via a set of wires, wherein the audio functional unit comprises an audio system, wherein the audio system includes the master clock, said audio functional unit comprising;

a serial port clocked according to the serial clock from the audio system, wherein the serial clock is at a clock rate and is derived from the master clock;

an audio functional circuitry coupled to the serial port, wherein the audio functional circuitry is programmable, provides a plurality of functions and is operable at a plurality of sample rates; and

rate selection control logic coupled to the audio functional circuitry and coupled to receive the serial clock and the master clock, wherein the rate selection control logic senses a ratio between the serial clock and the master clock and reprograms the audio functional circuitry to operate at one of the plurality of sample rates in response to a change in the clock rate of the serial clock, such that the audio functional circuitry operates at another of the plurality of sample rates.

16. The audio subsystem defined in claim 15 wherein the set of wires comprises only four conductors.

17. The audio subsystem defined in claim 16 wherein the set of wires comprises:

a first conductor transferring combined audio and command date from the serial I/O interface to the audio functional unit;

a second conductor transferring combined audio and status data from the audio functional unit to the serial I/O interface;

a third conductor transferring the serial clock; and

a fourth conductor transferring a synchronization signal.

18. The audio functional unit defined in claim 15 wherein the rate selection control logic comprises:

receiving means for receiving the master clock and the serial clock;

counter means coupled to the receiving means for incrementing a counter value in response to the master clock;

ratio latch means coupled to the counter means and the receiving means for receiving the counter value in response to the serial clock, wherein the counter value comprises an indication of the ratio of the master clock to the serial clock.

19. The audio functional unit defined in claim 18 further comprising initializing means for initializing the counter value to an initial value.

20. The audio functional unit defined in claim 19 where the initializing means includes a register.

21. The audio functional unit defined in claim 15 wherein the rate selection control logic comprises:

a receiver for receiving the master clock and the serial clock;

a counter coupled to the receiver, wherein the counter increments a counter value in response to the master clock;

a ratio latch coupled to the counter and the receiver for receiving the counter value in response to the serial clock, wherein the counter value comprises an indication of the ratio of the master clock to the serial clock.

22. The apparatus defined in claim 21 further comprising a controller coupled to the ratio latch and the counter, wherein the controller controls the loading of the ratio latch and the counter to cause the ratio latch to receive the counter value and the counter to receive the initial value, such that the counter value is loaded into the ratio latch prior to the initial value being loaded into the counter.

23. The apparatus defined in claim 15 wherein the rate selection control logic programs the audio functional circuitry by modifying decimation filters within the audio functional unit.