Spread spectrum communication and synchronization

1. A method for determining temporal synchronization of a plurality of electrically-coupled digital receivers, the method comprising:

receiving at an input of a single modulator circuit a data signal having a data rate;

modulating the data signal with a pseudo-noise code wherein the pseudo-noise code has a data rate that is greater than the data rate of the data signal;

communicating the modulated signal from the single modulator circuit to the plurality of digital receivers through a wireline connection;

receiving at the plurality of digital receivers the modulated data signal;

for each digital receiver:

generating a correlation values using the modulated data signal and the pseudo-noise code; and

comparing the correlation values to a predetermined value to determine if the data signal is temporally synchronized.

2. The method of claim 1 , wherein the pseudo-noise code when auto-correlated has a maximum peak at a single time shift.

3. The method of claim 1 , further comprising:

passing the correlation values which represent the demodulated data signal if comparing indicates temporal synchronization.

4. The method of claim 1 , further comprising sending an out-of-synchronization signal if comparing indicates out-of-synchronization.

5. The method of claim 1 , further comprising:

if comparing indicates out-of-synchronization, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation value of the data signal, and comparing the correlation value to the predetermined value until the comparison indicates synchronization.

6. The method of claim 1 , wherein the predetermined value is such that comparing indicates synchronization when a predetermined number of bit errors occur during a predetermined interval in the modulated data signal.

7. The method of claim 5 , wherein if the pseudo-noise code has been shifted through all bits of the code and no comparison indicates synchronization, sending a data error signal.

8. A system for temporally synchronizing data signals between electrically coupled digital systems, comprising:

a transmitter including an input for receiving a digital data signal having a data rate, a modulator for modulating the digital data signal with a pseudo-noise code having a data rate greater than the digital data signal, and an output for communicating the modulated digital data signal; and

a plurality of receivers electrically coupled through a wireline connection to the transmitter, each receiver having an input for receiving the modulated digital data signal, a demodulator for generating at least one correlation value using the pseudo-nouse code and the modulated digital data signal, a comparator for comparing the al least one correlation value to a predetermined value to determine temporal synchronization, and an output for passing the the at least one correlation value that represents the demodulated digital data signal.

9. The system of claim 8 , wherein the pseudo-noise code has an auto-correlation function having a maximum peak at one time shift.

10. The system of claim 8 , operated to pass the correlation value that represents the demodulated digital data signal if comparing the correlation value to the predetermined value indicates synchronization.

11. The system of claim 8 , operated to send an out-of-synchronization signal if comparing the correlation value to the predetermined value indicates out-of -synchronization.

12. The system of claim 8 , wherein the predetermined value is such that comparing the correlation value to the predetermined value indicates synchronization when a predetermined number of bit errors occur during a predetermined interval in the modulated data signal.

13. The system of claim 8 , further operated such that if comparing the correlation value to the predetermined value indicates out-of-synchronization, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation value of the data signal, and comparing the correlation value to the threshold value until the comparison indicates synchronization.

14. A method for determining if a data signal is temporally synchronized, the method comprising:

at a plurality of receivers in a wireline system:

receiving a data signal modulated with a pseudo-noise code and having a data rate from a modulator within the wireline system;

generating a correlation signal using the modulated data signal and the pseudo-noise code; and

comparing the correlation signal to a predetermined value for determining if the demodulated data signal is temporally synchronized.

15. The method according to claim 14 wherein the pseudo-noise code has a data rate that is greater than the data rate of the received data signal.

16. The method according to claim 14 , wherein the predetermined value is such that comparing will determine that the correlation value that is representative of the demodulated data signal is synchronized even if there is a transmission error during one period of the pseudo-noise code.

17. The method according to claim 14 , wherein the predetermined value is such that comparing will determine that the demodulated data signal is synchronized even if there is a transmission error during multiple periods of the pseudo-noise code.

18. The method according to claim 14 wherein if comparing determines that the demodulated data signal is not synchronized, repeatedly shifting the pseudo-noise code, demodulating the modulated data signal with the shifted pseudo-noise code, generating a correlation signal, and comparing the correlation signal with the predetermined value until comparing determines that the demodulated signal is temporally synchronized.

19. The method according to claim 18 , wherein if all shifted versions of the pseudo-noise code are used and comparing determines that the demodulated signal is not synchronized, outputting an error signal.

20. The method according to claim 18 wherein a new portion of the received data signal is used during demodulating with each shifted version of the pseudo-noise code.