Power management in a configurable bus

1. A system, comprising:

bus interface circuitry configured to interconnect to a bus; and

a component, coupled to the bus interface circuitry, the component comprising circuitry configured to:

responsive to a bus state of the bus, determine a period comprising a start and an end during which no data is sent to the component;

upon detection of a cleared presence bit by the component, cause the component to enter a sleep mode during the period, the cleared presence bit indicating that no data is present for the component; and

responsive to a set presence bit in a first received frame at the component, cause the component to initiate a waking process, the waking process comprising continually clearing a set value of a clear-to-send bit in a first sent frame until after the end of the period, the set presence bit indicating that there is data for the component; and

after clearing the set value of the clear-to-send bit in the first sent frame, indicate that the period has completed and the waking process has completed by allowing the set value of the clear-to-send bit to remain set for a predetermined number of consecutive sent frames.

2. The system of claim 1 , where the circuitry is further configured to determine the start of the period responsive to a clock pause sent over the bus.

3. The system of claim 2 , where the component is configured to receive the clock pause in response to a completion of a data transmission.

4. The system of claim 1 , where the circuitry is configured to determine the start of the period responsive to a flow control field, the flow control field included in a second received frame sent via the bus.

5. The system of claim 4 , where:

the flow control field comprises the cleared presence bit; and

the second received frame comprises a SLIMbus-compliant message, the cleared presence bit configured to indicate the start of the period.

6. A method, comprising:

determining a period in which no data is sent to a component over a bus period responsive to an asserted presence bit in a first received frame;

upon detection of a presence bit being in a first state indicating that no data is present for the component, causing the component to enter a sleep mode during the period;

upon detection of the presence bit being in a second state indicating that there is data for the component, causing the component to initiate a waking process, the waking process comprising continually clearing a set value of a clear-to-send bit in a first sent frame until an end of the period; and

after clearing the set value of the clear-to-send bit in the first sent frame, indicating that the period has completed and the waking process has completed by allowing the set value of the clear-to-send bit to remain set for a predetermined number of consecutive sent frames.

7. The method of claim 6 , where the bus period is for a bus and the bus comprises a configurable bus.

8. A product comprising:

a machine-readable medium other than a transitory signal; and

instructions stored on the machine-readable medium, the instructions, when executed, configured to cause a processor to:

determine a period in which no data is sent to a component over a bus;

upon detection of a cleared presence bit indicating that no data is present for the component, cause the component to enter a sleep mode during the period;

while the component is in the sleep mode, determine that the component is not ready to receive a transmission over the bus; and

responsive to an asserted presence bit in a first received frame indicating that there is data for the component, cause the component to initiate a waking process, the waking process comprising continually clearing a set value of a clear-to-send bit in a first sent frame; and

after clearing the set value of the clear-to-send bit in the first sent frame, indicating that the period has completed and the waking process has completed by allowing the set value of the clear-to-send bit to remain set for a predetermined number of consecutive sent frames.

9. The product of claim 8 , where the instructions are further configured to cause the processor to determine a start of the period responsive to a clock pause sent over the bus.

10. The product of claim 9 , where the instructions are further configured to cause the processor to receive the clock pause in response to a completion of a data transmission.

11. The product of claim 8 , where the instructions are further configured to cause the processor to determine a start of the period responsive to the cleared presence bit within a second received frame.

12. The method of claim 6 , where determining the period comprises determining a start of the period responsive to a cleared presence bit within a second received frame.

13. The system of claim 1 , where the bus is configured to support burst-mode transfers.

14. The system of claim 13 , where the period comprises a break in transmission created by opportunistic application of a burst-mode transfer.

15. The system of claim 1 , where the bus is configured to support pushed digital audio transport to the component.

16. The method of claim 6 , requesting a bus clock rate increase to effect an opportunistic burst mode transfer that creates the period which no data is sent to the component.

17. The method of claim 6 , where a start of the period comprises a completion of a pulled digital audio transport stream.

18. The product of claim 8 , where the component comprises an application processor coupled via the bus to audio circuitry, GPS circuitry, wireless networking circuitry, or any combination thereof.

19. The product of claim 8 , where the instructions are further configured to cause the processor to request a bus clock rate increase to effect an opportunistic burst mode transfer that creates the period which no data is sent to the component.

20. The product of claim 8 , where a start of the period comprises a completion of a pulled digital audio transport stream.