Graphics Accelerator

• US 20080049826A1
• Filed: 08/28/2007
• Published: 02/28/2008
• Est. Priority Date: 11/09/1998
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Arthur Abnous, David Kruse, Henry Samueli, John Creigh, Mehdi Hatamian, Oscar Agazzi
• Inventors: Creigh, John, Kruse, David, Hatamian, Mehdi, Samueli, Henry, Abnous, Arthur, Agazzi, Oscar
• Granted Patent: US 7,769,101 B2
• Time in Patent Office: Days
• US Class Current: 375/233
• CPC Class Codes: G01R 31/3004 Current or voltage test
• CPC Class Codes: G01R 31/3008 Quiescent current [IDDQ] test or leakage current test
• CPC Class Codes: G01R 31/3016 Delay or race condition test, e.g. race hazard test
• CPC Class Codes: G01R 31/31715 Testing of input or output circuits; test of circuitry between the I/C pins and the functional core, e.g. testing of input or output driver, receiver, buffer
• CPC Class Codes: G01R 31/318502 Test of Combinational circuits
• CPC Class Codes: G01R 31/318552 Clock circuits details
• CPC Class Codes: G01R 31/318594 Timing aspects clock circuits G01R31/318552
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 3/235 combined with adaptive equaliser
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0047 Decoding adapted to other signal detection operation in conjunction with sequence estimation or equalization H04L25/03286
• CPC Class Codes: H04L 1/0053 specially adapted for power saving
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/242 by comparing a transmitted test signal with a locally generated replica
• CPC Class Codes: H04L 2001/0096 Channel splitting in point-to-point links
• CPC Class Codes: H04L 2025/03363 Multilevel H04L2025/03369 takes precedence
• CPC Class Codes: H04L 2025/03369 Partial response
• CPC Class Codes: H04L 2025/03477 : not time-recursive
• CPC Class Codes: H04L 2025/0349 : as a feedback filter
• CPC Class Codes: H04L 2025/03496 : as a prediction filter
• CPC Class Codes: H04L 2025/03503 : as a combination of feedback and prediction filters
• CPC Class Codes: H04L 2025/03617 : Time recursive algorithms H04L2025/03643 takes precedence
• CPC Class Codes: H04L 2025/03745 : Timing of adaptation
• CPC Class Codes: H04L 25/03038 : with a non-recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03057 : with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03146 : with a recursive structure H04L25/03127 takes precedence
• CPC Class Codes: H04L 25/03197 : methods of calculation involving metrics
• CPC Class Codes: H04L 25/03203 : Trellis search techniques
• CPC Class Codes: H04L 25/03235 : with state-reduction using feedback filtering
• CPC Class Codes: H04L 25/03267 : with decision feedback equalisers
• CPC Class Codes: H04L 25/03987 : Equalisation for sparse channels
• CPC Class Codes: H04L 25/067 : providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 25/14 : Channel dividing arrangements , i.e. in which a single bit stream is divided between several baseband channels and reassembled at the receiver
• CPC Class Codes: H04L 25/4917 : using multilevel codes
• CPC Class Codes: H04L 25/497 : by correlative coding, e.g. partial response coding or echo modulation coding transmitters and receivers for partial response systems transversal equalizers at the transmitter end H04L25/03343
• CPC Class Codes: H04L 7/0062 : detection of error based on data decision error, e.g. Mueller type detection
• CPC Class Codes: H04L 7/0334 : Processing of samples having at least three levels, e.g. soft decisions

Abstract

Various systems and methods providing high speed decoding, enhanced power reduction and clock domain partitioning for a multi-pair gigabit Ethernet transceiver are disclosed. ISI compensation is partitioned into two stages; a first stage compensates ISI components induced by characteristics of a transmitters partial response pulse shaping filter in a demodulator, a second stage compensates ISI components induced by characteristics of a multi-pair transmission channel in a Viterbi decoder. High speed decoding is accomplished by reducing the DFE depth by providing an input signal from a multiple decision feedback equalizer to the Viterbi based on a tail value and a subset of coefficient values received from a unit depth decision-feedback equalizer. Power reduction is accomplished by adaptively truncating active taps in the NEXT, FEXT and echo cancellation filters, or by disabling decoder circuitry portions, as channel response characteristics allow. A receive clock signal is generated such that it is synchronous in frequency with analog sampling clock signals and has a particular phase offset with respect to one of the sampling clock signals. This phase offset is adjusted such that system performance degradation due to coupling of switching noise from the digital sections to the analog sections is substantially minimized.

Claims

1. An integrated circuit communication device configured for operation over a multi-pair transmission channel, the communication device comprising:

a decoder operable to decode a signal having N states, where N is an integer greater than one, and operable to generate tentative decisions regarding a path and a final decision;

a single-state decision feedback equalizer operable to receive the tentative decisions and to produce a single-state intersymbol interference (ISI) compensation signal corresponding to an ISI component based on the tentative decisions; and

a state multiplication circuit adapted to produce an N-state representation signal, suitable for decoding by the decoder, based on the single-state ISI compensation signal.

3. The integrated circuit communication device of claim 1 wherein the single-state decision feedback equalizer is operable to produce the single-state ISI compensation signal based on a subset of high-order coefficients.

8. The integrated circuit communication device of claim 1, wherein the single-state decision feedback equalizer has a substantially inverse impulse response to the impulse response of a pulse shaping filter of a remote transmitter, and wherein the integrated circuit communication device further comprises and adaptive gain stage.

2. (canceled)

4-7. -7. (canceled)

9. A method of processing a communication signal having N states and transmitted over a multi-pair transmission channel, where N is an integer greater than one, the method comprising steps of:

(a) generating tentative decisions regarding a path and a final decision;

(b) producing a single-state intersymbol interference (ISI) compensation signal corresponding to an ISI component based on the tentative decisions;

(c) producing an N-state representation signal based on the single-state ISI compensation signal; and

(d) decoding the N-State representation signal.

11. The method of claim 9 wherein producing step (b) comprises producing the single-state ISI compensation signal based on a subset of high-order coefficients.

10. (canceled)

12-15. -15. (canceled)

16. An integrated circuit communication device, the communication device comprising:

a decoder operable to decode a signal having a plurality of states, and generating tentative decisions regarding a path and a final decision;

a single-state decision feedback equalizer operable to receive the tentative decisions and to produce a single-state intersymbol interference (ISI) compensation signal corresponding to a first ISI component based on the tentative decisions; and

a state multiplication circuit operable to receive a tail component generated by subtracting the single-state ISI compensation signal from a signal sample and to produce a signal having a plurality states, suitable for decoding by the decoder, based on the tail component.

17. The integrated circuit communication device of claim 16 wherein the single-state decision feedback equalizer is operable to produce the single-state ISI compensation signal based on a subset of high-order coefficients.

18. The integrated circuit communication device of claim 17 wherein the state multiplication circuit is operable to produce the signal having a plurality of states, suitable for decoding by the decoder, based on the tail component and a subset of low-order coefficient values from the single-state decision feedback equalizer.

19. The integrated circuit communication device according to claim 18, further comprising a convolution engine coupled to the single-state decision feedback equalizer and operable to receive values of the low-order coefficients and to compute a set of pre-computed values representing a set of potential single-state ISI compensation signals corresponding to a second ISI component, wherein the state multiplication circuit is operable to produce the signal having a plurality of states based on the tail component and the set of pre-computed values.

20. The integrated circuit communication device of claim 19 wherein the multiplication circuit comprises a multiple-decision feedback equalizer coupled to the single-state decision feedback equalizer and the convolution engine, the multiple-decision feedback equalizer operable to combine the set of pre-computed values with the tail component to produce a set of potential digital signals, one of the potential digital signals being substantially compensated for the second ISI component.

21. The integrated circuit communication device of claim 20 wherein the first ISI component represents ISI introduced by a remote transmission device, and wherein the second ISI component represents ISI introduced by transmission channel characteristics.

22. A method of processing a communication signal having a plurality of states, the method comprising steps of:

(a) generating tentative decisions regarding a path and a final decision;

(b) producing a single-state intersymbol interference (ISI) compensation signal corresponding to a first ISI component based on the tentative decisions;

(c) subtracting the single-state ISI compensation signal from a signal sample to produce a tail component;

(d) producing a representation signal having a plurality of states based on the tail component; and

(e) decoding the representation signal.

23. The method of claim 22 wherein producing step (b) comprises producing the single-state ISI compensation signal based on a subset of high-order coefficients.

24. The method of claim 23 wherein producing step (d) comprises producing the representation signal based on the tail component and a subset of low-order coefficient values.

25. The method of claim 24 further comprising a step (f), performed prior to producing step (d), of computing a set of pre-computed values representing a set of potential single-state ISI compensation signals corresponding to a second ISI component, wherein producing step (d) comprises producing the representation signal based on the tail component and the set of pre-computed values.

26. The method of claim 25 wherein producing step (d) comprises combining the set of pre-computed values with the tail component to produce a set of potential digital signals, one of the potential digital signals being substantially compensated for the second ISI component.

27. The method of claim 26 wherein the first ISI component represents ISI introduced by a remote transmission device, and wherein the second ISI component represents ISI introduced by transmission channel characteristics.