Method and apparatus for selectable high performance or low power processor system
A communications processor is operative in a plurality of modes including at least a high performance mode, a power savings mode with lower computational capability, and a shutdown mode with a wakeup capability. A memory for the communications processor has a high speed segment and a low speed segment, the high speed segment and low speed segment respectively on a high speed data bus and a low speed data bus, the high speed data bus and low speed data bus coupled by a bidirectional bridge.
1. A processor comprising:
a central processing unit (CPU);
a performance controller having a performance register, the performance register having a plurality of values associated with incrementally increasing performance and incrementally increasing power consumption;
a high speed bus coupled to a low power static random access memory (LPSRAM), a high speed static random access memory (HSSRAM), and to the CPU;
a low speed bus coupled to the CPU and the performance register;
a bridge coupling the high speed bus to the low speed bus;
the performance controller, for each discrete value of performance register, associating a CPU voltage from a CPU voltage source, a CPU clock speed from a CPU clock source, and enabling or disabling the LPSRAM and HSSRAM;
the low speed bus coupled to an RF energy detector periodically storing samples of RF energy level into the LPSRAM, wherein an increase in the RF energy level of the samples causes the performance controller to change a value in the performance register to a higher performance level.
2. The processor of claim 1 where increasing a value in the performance register causes the CPU voltage and CPU clock to increase in sequence from approximately 0.7V and approximately 32 Mhz to approximately 0.9V and approximately 100 Mhz, or to approximately 1.1V and approximately 180 Mhz.
3. The processor of claim 1 where at least one of the performance register values provides a reduced HPSRAM or LPSRAM voltage for retention of data but where the reduced voltage does not provide for reading or writing data.
4. The processor of claim 1 where said CPU is coupled to a clock source which is at least one of a ring oscillator (RO) or a resistor/capacitor (RC) oscillator for a low power performance register value and a phase locked loop (PLL) oscillator for a high performance mode.
5. The processor of claim 1 where the performance register has values of PS0, PS1, PS2, PS3, and PS4, where, in sequence, each value provides greater power consumption and greater performance.
6. The processor of claim 5 where the performance register value of PS0 corresponds to a sleep mode.
7. A processor comprising:
a central processing unit (CPU);
a performance register having a plurality of values associated with incrementally increasing processor performance and incrementally increasing processor power consumption;
a high speed bus coupled to a low power static random access memory (LPSRAM), a high speed static random access memory (HSSRAM), and to the CPU;
a low speed bus coupled to the CPU and to the performance register;
a bridge coupling the high speed bus to the low speed bus;
the performance register, for each value, associating a CPU voltage from a CPU voltage source, a CPU clock speed from a CPU clock source, and enabling or disabling the LPSRAM and HSSRAM;
the performance register having a sleep mode value associated with a minimum power consumption;
the low speed bus coupled to an RF energy detector periodically storing samples of RF energy level into the LPSRAM when the performance register contains the sleep mode value, wherein an increase in the RF energy level of the samples causes the performance register to change to a higher performance level.
8. The processor of claim 7 where increasing the value in the performance register causes the CPU voltage and CPU clock to increase in sequence from approximately 0.7V and approximately 32 Mhz to approximately 0.9V and approximately 100 Mhz, or to approximately 1.1V and approximately 180 Mhz.
9. The processor of claim 7 where at least one of the performance register values provides a reduced HPSRAM or LPSRAM voltage for retention of data but where the reduced voltage does not provide for reading or writing data.
10. The processor of claim 7 where said CPU is coupled to a clock source which is at least one of a ring oscillator (RO) or a resistor/capacitor (RC) oscillator for a low power performance register value and a phase locked loop (PLL) oscillator for a high performance mode.
11. The processor of claim 7 where said performance register has values of PS0, PS1, PS2, PS3, and PS4, where, in sequence, each value provides greater power consumption and greater performance.
12. The processor of claim 7 where the performance register is configured to detect a performance level and change a value in the performance register to a value associated with a higher performance level when a higher performance level is required, and change a value in the performance register to a value associated with a lower performance level when a lower performance level is required.
13. A processor comprising:
a central processing unit (CPU);
a performance register having a plurality of states, each state associated with a particular level of performance and power consumption;
a performance register controller configured to dynamically adjust the performance register;
a processor clock source having an output coupled to the CPU and having a frequency controlled by the performance register;
a voltage source coupled to the CPU, the voltage source controlled by the performance register, each voltage coupled to the CPU also associated with the a minimum voltage required to ensure operation of the CPU at each particular clock frequency selected by the performance register;
a high speed bus coupled to the CPU, the a high speed RAM, and also to a low power RAM;
a low power bus coupled to the CPU and also coupled to the performance register, the low power bus also coupled to a packet energy detector periodically sampling an RF energy level and storing the samples in a low power static random access memory (LPSRAM);
a bridge coupling between the high speed bus and low power bus;
the processor clock source comprising at least one of a ring oscillator or resistor/capacitor (RC) oscillator enabled for a low power state and a PLL enabled for a high performance state;
the CPU periodically waking up from a power savings mode and examining the stored samples, the CPU changing the performance register to a higher performance state when an increase in RF energy level is detected in the stored samples.
14. The processor of claim 13 where the power savings mode is a sleep mode during which the high speed bus is disabled and the voltage source selects a minimum voltage compared to other voltage source settings.
15. The processor of claim 13 where the power savings mode is a sleep mode with the clock source outputting a minimum clock frequency compared to other clock source frequencies.
16. The processor of claim 13 where the controller is operative to detect a timed interrupt or external event to change the performance register state.
17. The processor of claim 13 where the performance register states includes at least one of: a sleep state, a standby state, and low power operation state.
18. The processor of claim 16 where the performance register is written by the CPU.
19. The processor of claim 13 where a wireless media access controller (MAC) is coupled to the high speed bus.
20. The processor of claim 13 where the low power RAM operates at a reduced voltage for data retention when the performance register state is a sleep state.