# US 10,771,295 B2 · High speed signaling system with adaptive transmit pre-emphasis

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- Number: US 10,771,295 B2
- Document ID: US10771295B2
- Status: Granted
- Kind: B2
- Application number: 16/548,708
- Filed: 2019-08-22
- Published: 2020-03-12
- Granted: 2020-09-08
- Earliest claimed: 2003-12-17
- Assignees: Rambus Inc.
- Applicants: Rambus Inc.
- Inventors: Vladimir M. Stojanovic; Andrew C. Ho; Anthony Bessios; Fred F. Chen; Elad Alon; Mark A. Horowitz
- Web page: https://patentgrep.com/patent/US10771295B2

## CPC

- H04L 25/49: using code conversion at the transmitter; using predistortion; using insertion of idle bits for obtaining a desired frequency spectrum; using three or more amplitude levels {; Baseband coding techniques specific to data transmission systems (spectral shaping H04L25/03828)}
- H04B 1/04: Circuits
- H04B 1/0475: {with means for limiting noise, interference or distortion (H04B1/0483 takes precedence)}
- H04L 25/025: {using least-mean-square [LMS] method}
- H04L 25/028: {Arrangements specific to the transmitter end}
- H04L 25/03019: {adaptive, i.e. capable of adjustment during data reception}
- H04L 25/03343: {Arrangements at the transmitter end}
- H04L 25/03885: {adaptive}
- H04L 25/061: {providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of DC offset (removal of DC offset in coupling arrangements H04L25/029, H04L25/0296)}
- H04L 25/4917: {using multilevel codes}
- H04B 2001/0416: {having gain or transmission power control}
- H04L 25/0282: {Provision for current-mode coupling}
- H04L 2025/03363: {Multilevel (H04L2025/03369 takes precedence)}
- H04L 2025/03802: {Signalling on the reverse channel}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04B: TRANSMISSION

## Abstract

A high-speed signaling system with adaptive transmit pre-emphasis. A transmit circuit has a plurality of output drivers to output a first signal onto a signal path. A receive circuit is coupled to receive the first signal via the signal path and configured to generate an indication of whether the first signal exceeds a threshold level. A first threshold control circuit is coupled to receive the indication from the receive circuit and configured to adjust the threshold level according to whether the first signal exceeds the threshold level. A drive strength control circuit is coupled to receive the indication from the receive circuit and configured to adjust a drive strength of at least one output driver of the plurality of output drivers according to whether the first signal exceeds the threshold level.

## Claims

### Claim 1

An apparatus, comprising:
a receiver to receive a digital sequence from a set of drivers over a serial link connecting the receiver to a transmitting device, the digital sequence equalized by a transmit equalizer in association with a plurality of taps; and
tap generation circuitry to generate tap information for setting at least one tap weight associated with at least one of the plurality of taps of the transmit equalizer, each tap weight comprising a driver strength value for a given tap, the tap information for at least one of the plurality of taps for use in transmitting across the serial link connecting the receiver to the transmitting device, the tap information configured to ensure that magnitudes of the tap weights associated with the plurality of taps of the transmit equalizer satisfy a predefined constraint; and
a transmitter to transmit the tap information to the set of drivers of the transmitting device.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein:
the digital sequence comprises a training sequence of symbols.

### Claim 3 (depends on 2)

The apparatus according to claim 2, wherein:
the training sequence of symbols is received by the receiver during an initialization mode of operation.

### Claim 4 (depends on 1)

The apparatus according to claim 1, wherein:
the tap information represents a change to at least one of the plurality of taps.

### Claim 5 (depends on 1)

The apparatus according to claim 1, wherein:
each tap weight value includes a sign and magnitude value.

### Claim 6 (depends on 1)

The apparatus according to claim 1, wherein:
the plurality of taps include a main tap, a pre-cursor tap, and a post-cursor tap.

### Claim 7 (depends on 6)

The apparatus according to claim 6, wherein:
the tap information is further configured based on a bit error rate (BER) value.

### Claim 8

A method of operation within a signaling system, the method comprising:
receiving a digital sequence with a receiver over a serial link connecting the receiver to a transmit equalizer, the transmit equalizer having a plurality of taps;
configuring tap information for at least one of the plurality of taps, the tap information for setting at least one tap weight associated with at least one of the plurality of taps of the transmit equalizer, each tap weight comprising a driver strength value for a given tap and including a sign and magnitude value, the configuring ensuring that the magnitudes of the tap weights associated with the plurality of taps satisfy a predefined constraint;
transmitting, to the transmit equalizer, the tap information; and
wherein a tap weight associated with the at least one of the plurality of taps is updated responsive to the transmitted tap information.

### Claim 9 (depends on 8)

The method according to claim 8, further comprising:
entering an initialization mode of operation; and
performing the receiving, configuring and transmitting during the initialization mode of operation.

### Claim 10 (depends on 8)

The method according to claim 8, wherein receiving the digital sequence comprises:
receiving a training sequence of symbols.

### Claim 11 (depends on 8)

The method according to claim 8, wherein:
the tap information represents a change to at least one of the plurality of taps.

### Claim 12 (depends on 8)

The method according to claim 8, wherein:
the tap information represents a tap weight value for substitution for at least one of the plurality of taps.

### Claim 13 (depends on 8)

The method according to claim 8, wherein:
the plurality of taps include a main tap, a pre-cursor tap, and a post-cursor tap.

### Claim 14 (depends on 13)

The method according to claim 13, wherein the configuring further comprises:
determining a bit error rate (BER) associated with the received digital sequence; and
configuring the tap information based on the BER.

### Claim 15

An integrated circuit (IC) chip, comprising:
a receiver to receive a training sequence of symbols during an initialization mode over a serial link connecting the receiver to a transmit equalizer, the transmit equalizer having at least one tap; and
tap generation circuitry to generate tap information, the tap information for setting at least one tap weight associated with at least one of the plurality of taps of the transmit equalizer, each tap weight comprising a driver strength value for a given tap including a sign and magnitude value, the tap information for the at least one tap configured to ensure that the magnitudes of the tap weights associated with the plurality of taps of the transmit equalizer satisfy a predefined constraint; and
a transmitter to transmit the tap information to the transmit equalizer.

### Claim 16 (depends on 15)

The IC chip according to claim 15, wherein:
the tap information represents a change to at least one of the plurality of taps.

### Claim 17 (depends on 15)

The IC chip according to claim 15, wherein:
the tap information represents a tap weight value for substitution for at least one of the plurality of taps.

### Claim 18 (depends on 15)

The IC chip according to claim 15, wherein:
the plurality of taps include a main tap, a pre-cursor tap, and a post-cursor tap.

### Claim 19 (depends on 15)

The IC chip according to claim 15, wherein:
the tap information is further configured based on an error value.

### Claim 20 (depends on 19)

The IC chip according to claim 19, wherein:
the error value comprises a bit error rate (BER).