Methods and apparatus for transceiver power noise reduction

1. A method of serial data communication, the method comprising:

encoding data to be transmitted by a communication protocol encoder of a transmitter to generate protocol-encoded data;

serializing the protocol-encoded data to generate serialized data;

encoding the serialized data for power-delivery-network noise reduction (PNR) using a PNR encoder so as to generate PNR-encoded serial data;

providing the serialized data to a first input of a first selector;

providing the PNR-encoded serial data to a second input of the first selector;

outputting the serialized data by the first selector when a first control signal indicates a first operating mode in which said encoding is disabled;

outputting the PNR-encoded serial data by the first selector when the first control signal indicates a second operating mode in which said encoding is enabled;

driving onto a communication channel the serialized data signal in the first operating mode and the PNR-encoded serial data signal in the second operating mode.

2. The method of claim 1 , wherein encoding the serialized data for power-delivery-network noise reduction is performed using a linear feedback shift register having a cascade of flip-flop circuits which includes a first flip-flop circuit, an interior flip-flop circuit, and a last flip-flop circuit, and wherein outputs of the interior flip-flop circuit and the last flip-flop circuit are provided to an input of the first flip-flop circuit, the method further comprising:

determining a resonance characteristic of power-delivery-network noise that couples through power rails to the transmitter, and

selecting the interior flip-flop from a plurality of flip-flop circuits in an interior of the cascade depending on said resonance characteristic of the power-delivery-network noise.

3. The method of claim 1 , wherein encoding the serialized data for power-delivery-network noise reduction is performed using a selectively-enabled sequence generator that encodes portions of the serialized data while other portions of the serialized data remain unencoded.

4. The method of claim 3 , further comprising:

determining a resonant frequency of power-delivery-network noise that couples through power rails to the transmitter, and

enabling the selectively-enabled sequence generator periodically to reduce the power-delivery-network noise at the resonant frequency.

5. The method of claim 1 , further comprising:

receiving data signal driven from the communication channel by a buffer at a receiver;

decoding the received data signal by a PNR decoder to obtain PNR-decoded received data;

providing the received data signal to a first input of a second selector;

providing the PNR-decoded received data to a second input of the second selector;

outputting the received data signal by the second selector when a second control signal indicates the first operating mode;

outputting the PNR-decoded received data by the second selector when the second control signal indicates the second operating mode;

deserializing selected data output from the second selector to re-generate the protocol-encoded data; and

decoding the protocol-encoded data by a communication protocol decoder to re-generate the data to be transmitted.

6. The method of claim 5 ,

wherein encoding the serialized data for PNR is performed using a first linear feedback shift register at the transmitter, and decoding the PNR-encoded serial data is performed using a second linear feedback shift register at the receiver, and

wherein each of the first and second linear feedback shift registers comprises a cascade of flip-flop circuits which includes a first flip-flop circuit, an interior flip-flop circuit, and a last flip-flop circuit, and wherein outputs of the interior flip-flop circuit and the last flip-flop circuit are provided to an input of the first flip-flop circuit,

the method further comprising:

determining a resonance characteristic of power-delivery-network noise that couples through power rails to the transmitter, and

selecting the interior flip-flop from a plurality of flip-flop circuits in an interior of the cascade depending on said resonance characteristic of the power-delivery-network noise.

7. The method of claim 5 , wherein encoding the serialized data for PNR is performed using a first selectively-enabled sequence generator at the transmitter, and decoding the PNR-encoded serial data is performed using a second selectively-enabled sequence generator at the receiver, and wherein each of the first and second selectively-enable sequence generators encodes portions of the serialized data while other portions of the serialized data remain unencoded.

8. The method of claim 7 , further comprising:

determining a resonant frequency of power-delivery-network noise that couples through power rails to the transmitter, and

enabling the selectively-enabled sequence generator periodically to reduce the power-delivery-network noise at the resonant frequency.

9. An apparatus for serial data communication, the apparatus comprising:

a communication protocol encoder that encodes data to be transmitted so as to generate protocol-encoded data;

a serializer that serializes the protocol-encoded data to generate serialized data;

a power-delivery-network noise reduction (PNR) encoder that encodes the serialized data to generate PNR-encoded serial data;

a first selector that receives the serialized data at a first input and the PNR-encoded serial data at a second input and that is controlled by a first control signal such that the serialized data is output when the first control signal is in a first state and the PNR-encoded serial data is output when the first control signal is in a second state, wherein the first state indicates a first operating mode in which the PNR encoder is disabled, and the second state indicates a second operating mode in which the PNR encoder is enabled;

a driver circuit that drives data output from the first selector onto a communication channel such that the serialized data is driven onto the communication channel in the first operating mode and the PNR-encoded serial data is driven onto the communication channel in the second operating mode.

10. The apparatus of claim 9 , wherein the PNR encoder comprises a linear feedback shift register.

11. The apparatus of claim 9 , wherein the PNR encoder comprises a selectively-enabled sequence generator.

12. The apparatus of claim 11 , wherein the selectively-enabled sequence generator periodically generates a sequence of alternating bits.

13. The apparatus of claim 9 , further comprising:

a buffer at a receiver that receives data output driven from the communication channel;

a PNR decoder that decodes the received data output to obtain PNR-decoded received data;

a second selector that receives the received data output at a first input and the PNR-decoded received data at a second input and that is controlled by a second control signal such that the received data output is output when the second control signal is in a first state and the PNR-decoded received data is output when the second control signal is in a second state;

a deserializer that deserializes selected data output from the second selector to re-generate the protocol-encoded data; and

a communication protocol decoder configured to decode the protocol-encoded data to re-generate the data to be transmitted.

14. The apparatus of claim 13 , wherein the PNR encoder comprises a first linear feedback shift register, and the PNR decoder comprises a second linear feedback shift register.

15. The apparatus of claim 13 , wherein the PNR encoder comprises a first selectively-enabled sequence generator, and the PNR decoder comprises a second selectively-enabled sequence generator.

16. The apparatus of claim 15 , wherein the first and second selectively-enabled sequence generators each periodically generates a sequence of alternating bits.

17. A serial communication system, the system comprising:

a transmitter, the transmitter further comprising:

a serializer that serializes a protocol-encoded data to generate serialized data,

a power-delivery-network noise reduction (PNR) encoder that encodes serialized data to generate PNR-encoded serial data,

a first selector that selectively outputs the serialized data in a first operating mode and the PNR-encoded serial data in a second operating mode, and

a driver circuit that drives data output by the first selector onto a communication channel; and

a receiver, the receiver further comprising:

a buffer that receives data output driven from the communication channel,

a PNR decoder that decodes the received data output to obtain PNR-decoded received data,

a second selector that selectively outputs the received data output in the first operating mode and the PNR-decoded received data in the second operating mode, and

a deserializer that deserializes the selected data output from the second selector to re-generate the protocol-encoded data.

18. The system of claim 17 , wherein the PNR encoder comprises a first linear feedback shift register, and the PNR decoder comprises a second linear feedback shift register.

19. The system of claim 17 , wherein the PNR encoder comprises a first selectively-enabled sequence generator, and the PNR decoder comprises a second selectively-enabled sequence generator.

20. The system of claim 19 , wherein the first and second selectively-enabled sequence generators are each configured to periodically generate a sequence of alternating bits.