Transceiver clock architecture with transmit PLL and receive slave delay lines

Abstract

A method and apparatus for transceiver clock architecture with transmit PLL and receive slave delay lines. In one embodiment, the method includes the generation of a transmitter (Tx) clock signal by adjusting a control voltage of a voltage controlled oscillator to lock a phase and frequency of Tx clock signal to a reference clock signal. In one embodiment, a frequency of the Tx clock signal is a multiple of a frequency of the reference clock signal. In one embodiment, a slave delay line may be used, including a plurality of variable delay buffers that are configured according to the control voltage to generate a receiver (Rx) clock signal in response to a received clock signal that is synchronized with the reference clock signal. The Rx clock signal may be provided to data recovery logic to sample data. Other embodiments are described and claimed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:

FIG. 1 is a block diagram illustrating a computer system, including a transceiver clock architecture with a transmitter phase locked loop (PLL) and one or more receiver slave delay lines, in accordance with one embodiment.

FIG. 2 is a block diagram further illustrating the transceiver shown in FIG. 1, in accordance with one embodiment.

FIGS. 3A and 3B are clock diagrams to illustrate multi-phase transmitter clock generation and multi-phase receiver clock generation for data recovery, according to one embodiment.

FIG. 4 is a block diagram illustrating a computer system to provide dual phase clocking using a transceiver clock architecture, including a transmitter PLL and one or more receiver slave delay lines, according to one embodiment

FIG. 5 illustrates a computer system, including a CPU including a transceiver for communicating with a chipset transceiver, for example, as shown in FIGS. 1 and 2, according to one embodiment.

FIG. 6 is a block diagram illustrating various design representations or formats for simulation, emulation and fabrication of a design using the disclosed techniques.

DETAILED DESCRIPTION

A method and apparatus for transceiver clock architecture with transmitter (Tx) phase locked loop (PLL) and receiver (Rx) slave delay lines (SDL) are described. In one embodiment, the method includes the generation of a transmitter (Tx) clock signal that is locked to a reference clock according to a control voltage. In one embodiment, the Tx clock signal is generated by adjusting a control voltage of a voltage controlled oscillator to lock a phase and frequency of Tx clock signal to a reference clock signal. In one embodiment, a frequency of the Tx clock signal is a multiple of a frequency of the reference clock signal.

In one embodiment, a simplified transceiver clock architecture includes a slave delay line having a plurality of variable delay buffers, which are configured according to the control voltage. Once configured, the slave delay line may generate a receiver (Rx) clock signal in response to a received clock signal. The Rx clock signal may be provided to data recovery logic to sample data according to the Rx clock signal that is adjusted by the slave delay line to synchronize with the reference clock signal.

In the following description, numerous specific details such as logic implementations, sizes and names of signals and buses, types and interrelationships of system components, and logic partitioning/integration choices are set forth in order to provide a more thorough understanding. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures and gate level circuits have not been shown in detail to avoid obscuring the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate logic circuits without undue experimentation.

In the following description, certain terminology is used to describe features of the invention. For example, the term “logic” is representative of hardware and/or software configured to perform one or more functions. For instance, examples of “hardware” include, but are not limited or restricted to, an integrated circuit, a finite state machine or even combinatorial logic. The integrated circuit may take the form of a processor such as a microprocessor, application specific integrated circuit, a digital signal processor, a micro-controller, or the like.

FIG. 1 is a block diagram illustrating a computer system 100, including a first chip (Chip A) 102 and a second chip (Chip B) 170, where each chip includes a transceiver 200 with a transmitter phased locked loop (PLL) 210 and one or more receiver slave delay lines (SDL) 230, according to one embodiment. Representatively, chip 102 and chip 170 are coupled together via interconnect 108. In one embodiment, interconnect 108 may refer to a point-to-point link for enabling simultaneous bi-directional (SBD) differential signaling.

As shown in FIG. 1, interconnect 108 enables transceiver interfaces 200 to operate according to a source synchronous protocol, where a clock is forwarded, along with data, obviating the need for distribution of a global clock. Conventionally, source synchronous interfaces use a PLL to generate a transmitter clock and a separate DLL to generate a receiver clock. These conventional architectures suffer from high area and power consumption, resulting from the two complete closed loop circuits required to implement the PLL to generate the transmitter clock and the separate DLL to generate the receiver clock. The high area and power consumption is consumed by the two complete closed loop circuits with their accompanying filters, phase detectors and support logic.

In contrast to such dual loop architectures, FIG. 1 illustrates a single closed loop transceiver clock architecture 200, which is advantageous from an area and power efficiency perspective. Representatively, each transceiver interface 200 includes a single closed loop implemented as a phase locked loop (PLL) 210 to control clock generation. Representatively, functionality of the transceiver clock architecture, as shown in FIG. 1, requires a single crystal for implementation of clock generator 104 for generation of reference clock signal 106. For ease of understanding, like components between chip 102 and chip 170 are numbered using matching reference numbers.

In the embodiment illustrated, PLL 210 is provided to generate all transmit clocks and to control the delay of multiple slave delay lines (SDL) 230. In one embodiment, PLL 210 may generate multi-phase transmit clocks, whereas SDL 230 generates multi-phase clocks for receiver data recovery. In the embodiment illustrated, PLL 210 generates a transmitter (Tx) clock signal 226/232. In one embodiment, Tx clock signal 226/232 is a high-speed clock signal having a frequency that is a multiple of a frequency of reference clock 106.

In one embodiment, PLL 210, as further illustrated in FIG. 2, may divide the Tx clock signal 226/232 to match a phase and frequency of a divided Tx clock signal with a phase and frequency of reference clock signal 106 by adjusting a control voltage of a voltage controlled oscillator (VCO). A final value of the control voltage (Vctrl) 212 is passed to slave delay line 230. As described herein, adjusting of Vctrl 212 is performed to generate a frequency and phase lock between Tx clock signal 226/232 and reference clock signal 106.

Representatively, Tx clock signal 226/232 is provided to clock transmitter (CkTx) 264 to enable transmitter (Tx) 260 to transmit data 252/262 according to Tx clock signal 226/232. In response to Vctrl signal 212, SDL 230, which may include a delay cell circuit, including a plurality of delay buffers, may be configured as dictated by the Vctrl voltage 212 to generate a receiver (Rx) clock signal 236, which is provided to receiver (Rx) 250 to enable data recovery of received data 252/262.

FIG. 2 is a block diagram further illustrating PLL 210 and SDL 230, as shown in FIG. 1, according to one embodiment. Representatively, PLL 210 includes correction block 214, which may include a phase and frequency detector (PFD), a charge pump (CP) and a low path filter (LPF). Additional features regarding the PFD, CP and LPF of correction logic 214 are omitted to avoid obscuring details of the various embodiments.

As further shown in FIG. 2, PLL 210 may include a voltage controlled oscillator (VCO) 220 comprised of delay cell circuit 222. In one embodiment, delay cell circuit 222 includes a plurality of variable delay buffers, which are controlled by control voltage (Vctrl) 212. In one embodiment, delay cell circuit 220 includes feedback loop 224 to enable the generation of an oscillation frequency, as desired. Accordingly, in operation, a transmitter or Tx clock signal 226/232 is generated by setting the various delay buffer values according to the Vctrl signal 212. The Tx clock signal 226/232 is then divided by divider circuit 216 to match a frequency of reference clock signal 106.

Representatively, correction circuit 214 adjusts Vctrl signal 212 until a phase and frequency of a divided transmitter clock signal matches a frequency and phase of reference clock signal 106. Once matched, Tx clock signal 226/232 may be provided to clock transmitter circuits 264, as shown in FIG. 1. As further illustrated in FIG. 2, PLL 210 may include phase selection buffer 224, which enables the selection of a signal from the one or more buffers of delay cell circuit 220 to provide a multi-phase, or N-phase, Tx clock signal 226/232.

In the embodiment illustrated, control voltage 212 is provided to slave delay lines 230 (230-1, 230-2, . . . ). In one embodiment, delay cell circuits 240 of each slave delay line 230 are matched with delay cell circuit 222 of VCO 220 of PLL 210. Accordingly, in one embodiment, proper operation requires that SDL 230 is matched to VCO 220 of PLL 210 in all respects, including delay cell circuit design, input edge rate, input swing, output loading and physical layout. Assuming such constraints are met, SDL 230 generates accurate single or multi-phase outputs for phase interpolation and multi-phase clock distribution.

In one embodiment, a frequency of the incoming Rx clock is required to be equal to a frequency of the PLL output for proper multi-phase clock generation. Accordingly, by matching delay cell circuit 240 with delay cell circuit 222 of VCO 220, Rx clock signal 236 generated by each SDL is synchronized to a reference clock frequency to enable proper data recovery.

As further illustrated in FIG. 2, output buffer stage 234 of each SDL enables the generation of a multi-phase output, as dictated by PLL 210, for example, as illustrated with reference to FIGS. 3A and 3B.

FIGS. 3A and 3B illustrate timing diagrams for multi-phase transmitter clock generation and multi-phase receiver clock generation, according to one embodiment. Representatively, FIG. 3A illustrates timing diagram 262, which includes transmitter clock (TX Clk) 226-1/232-1 having a zero phase and Tx clock 226-2/232-2 having a 90° phase difference from Tx Clk 226-1/232-1. In the embodiment illustrated, delay 268 between Tx Clks 226-1/232-1 and 226-2/232-2 is controlled by PLL 210, as shown in FIGS. 1 and 2. Accordingly, in the embodiment illustrated, quadrature multi-phase clocking is provided to enable data sampling, as shown in FIG. 3B. Although quadrature, multi-phase clocking is shown, any desired phase difference may be provided as desired by the timing convention.

FIG. 3B is a timing diagram 256 illustrating the generation of multi-phase receiver clocks to enable proper data sampling, according to one embodiment. As illustrated, Rx data sample points 254 are required to enable proper data recovery. As shown, Rx clock 236-1 is provided having a zero phase, whereas Rx clock 236-2 is 90° out of phase with Rx clock 236-1. In one embodiment, the delay between Rx clocks (as generated by SDL 230) is controlled by PLL 210. Representatively, data recovery logic of a receiver may sample even data items on the rising edge and falling edge of Rx clock 236-1, while odd data items are sampled on the rising edge and falling edge of Rx clock 236-2.

FIG. 4 is a block diagram illustrating a computer system 300, including a transceiver clock architecture having a transmit PLL 310 and a plurality of receiver slave delay lines (SDL) 230, according to one embodiment. Representatively, PLL 310 is configured as shown in FIGS. 1 and 2. However, in the embodiment illustrated, a phase interpolator block 372-1 may couple one or more phase interpolators to receive a multi-phase output from PLL 310. In one embodiment, phase interpolator block 372-1 may perform phase interpolation of a multi-phase output for performing deskew. As further illustrated, phase interpolator block 372-1 may drive a local clock tree 374-2 and 374-6 for transmitter circuits 360-1 and 360-2, as well as clock transmitter circuits 364.

As further illustrated in FIG. 4, each SDL 330 (330-1, 330-2, 330-3 and 330-4) is coupled to a respective phase interpolator block 372. Representatively, phase interpolator blocks (372-2, 372-3, 372-4, 372-5) receive a multi-phase output from SDL 330, whereas phase interpolator block 372-1 receives a multi-phase output from PLL 310. In the embodiment illustrated, interpolator blocks 372-2 and 372-3 provide a dual phase clock for local clock trees 374-1 and 374-5. Representatively, local clock trees 374-1 and 374-5 may provide the multi-phase clock to receiver circuits 350-1 and 350-2 to enable data recovery.

Although illustrated to provide a dual phase clock, it should be recognized that the embodiment in FIG. 4 is provided to illustrate one embodiment and should not be interpreted in a limiting sense to dual phase clocking, as the various embodiments may apply to single-phase or multi-phase clocking, as desired for the particular system implementation.

Accordingly, in the embodiment illustrated in FIG. 4, PLL 310 is provided to generate a low jitter transmit clock, as well as to provide a multi-phase output for phase interpolation and dual clock distribution, as well as serving as a master circuit for SDLs 330. Accordingly, utilizing a transceiver interface configuration, for example as shown in FIG. 2, overhead of close loop design is minimized by using a single loop to control both Rx and Tx multi-phase clocking and phase interpolation for deskew.

FIG. 5 is a block diagram illustrating computer system 400 including transceiver interface 200 (200-1, 200-2, 200-3) including a transmitter (Tx) PLL and one or more receiver (Rx) slave delay lines (SDL), as shown in FIGS. 1, 2 and 4, in accordance with one embodiment. Representatively, computer system 400 comprises a processor system bus (front side bus (FSB)) 408 for communicating information between processor (CPU) 402 and chipset 470. As described herein, the term “chipset” is used in a manner to collectively describe the various devices coupled to CPU 402 to perform desired system functionality. In one embodiment, CPU 402 may be a multicore chip multiprocessor (CMP). In one embodiment, power source (battery) 401 is provided for operation as a mobile personal computer (MPC) system.

Representatively, chipset 470 may include memory controller hub 480 (MCH) coupled to graphics controller 484 via interconnect 485. In an alternative embodiment, graphics controller 484 is integrated into MCH 480, such that, in one embodiment, MCH 480 operates as an integrated graphics MCH (GMCH). Representatively, MCH 480 is also coupled to main memory 482 (482-1, . . . 482-2) via interconnect 483. In one embodiment, main memory 482 may include, but is not limited to, random access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), synchronous DRAM (SDRAM), double data rate (DDR) SDRAM (DDR-SDRAM), Rambus DRAM (RDRAM) or any device capable of supporting high-speed buffering of data.

As further illustrated, chipset 470 includes an input/output (I/O) controller hub (ICH) 490 coupled to MCH 480 via interconnect 471. Representatively, ICH 490 may couple a universal serial bus (USB) link or interconnect 494 to couple one or more USB slots (not shown) to ICH 490. Likewise, a serial advance technology attachment (SATA) 487 may couple hard disk drive devices (HDD) 486 to ICH 490. In one embodiment, basic input/output system (BIOS) 489 stored within flash memory 488 initializes computer system 400. Although chipset 470 is illustrated as including a separate MCH 480 and ICH 490, in one embodiment, MCH 480 may be integrated within CPU 402. In an alternate embodiment, the functionality of MCH 480 and ICH 490 are integrated within chipset 470.

In one embodiment, transceiver 200 may be implemented within computer systems including an MCH integrated within a CPU, an MCH and ICH integrated within a chipset, as well as a system on-chip. Accordingly, those skilled in the art recognize that FIG. 5 is provided to illustrate one embodiment and should not be construed in a limiting manner. In one embodiment, MCH 480 includes transceiver interface 200 for point-to-point link 408.

Representatively, in one embodiment, link 408 may support a serial interconnect protocol link protocol including, but not limited to, common system Interface (CSI), peripheral component interconnect (PCI) Express (PCI-E), SATA, SAS, Fibre-Channel, XAUI or other like serial interconnect. Accordingly, although one or more of the embodiments described herein may be provided with reference to CSI, those skilled in the art should recognize that the embodiments described herein are not limited to serial links, which support CSI, and are therefore applicable to other serial link protocols.

FIG. 6 is a block diagram illustrating various representations or formats for simulation, emulation and fabrication 530 of a design using the disclosed techniques. Data representing a design may represent the design in a number of manners. First, as is useful in simulations, the hardware may be represented using a hardware description language, or another functional description language, which essentially provides a computerized model of how the designed hardware is expected to perform. The hardware model 510 may be stored in a storage medium 500, such as a computer memory, so that the model may be simulated using simulation software 520 that applies a particular test suite 530 to the hardware model to determine if it indeed functions as intended. In some embodiments, the simulation software is not recorded, captured or contained in the medium.

Additionally, a circuit level model with logic and/or transistor gates may be produced at some stages of the design process. The model may be similarly simulated some times by dedicated hardware simulators that form the model using programmable logic. This type of simulation taken a degree further may be an emulation technique. In any case, reconfigurable hardware is another embodiment that may involve a machine readable medium storing a model employing the disclosed techniques.

Furthermore, most designs at some stage reach a level of data representing the physical placements of various devices in the hardware model. In the case where conventional semiconductor fabrication techniques are used, the data representing the hardware model may be data specifying the presence or absence of various features on different mask layers or masks used to produce the integrated circuit. Again, this data representing the integrated circuit embodies the techniques disclosed in that the circuitry logic and the data can be simulated or fabricated to perform these techniques.

In any representation of the design, the data may be stored in any form of a machine readable medium. An optical or electrical wave 560 modulated or otherwise generated to transport such information, a memory 550 or a magnetic or optical storage 540, such as a disk, may be the machine readable medium. Any of these mediums may carry the design information. The term “carry” (e.g., a machine readable medium carrying information) thus covers information stored on a storage device or information encoded or modulated into or onto a carrier wave. The set of bits describing the design or a particular of the design are (when embodied in a machine readable medium, such as a carrier or storage medium) an article that may be sealed in and out of itself, or used by others for further design or fabrication.

ALTERNATE EMBODIMENTS

It will be appreciated that, for other embodiments, a different system configuration may be used. For example, while the system 100 includes a single CPU 402, for other embodiments, a chipset multiprocessor (CMP) system including a plurality of processor cores or a multiprocessor system (where one or more processors may be similar in configuration and operation to the CPU 402 described above) may benefit from the two micro-operation flow using source override of various embodiments. Further different type of system or different type of computer system such as, for example, a server, a workstation, a desktop computer system, a gaming system, an embedded computer system, a blade server, etc., may be used for other embodiments.

Elements of embodiments of the present invention may also be provided as a machine-readable medium for storing the machine-executable instructions. The machine-readable medium may include, but is not limited to, flash memory, optical disks, compact disks-read only memory (CD-ROM), digital versatile/video disks (DVD) ROM, random access memory (RAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic or optical cards, propagation media or other type of machine-readable media suitable for storing electronic instructions. For example, embodiments described may be downloaded as a computer program which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a modem or network connection).

It should be appreciated that reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments.

In the above detailed description of various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which are shown by way of illustration, and not of limitation, specific embodiments in which the invention may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. The embodiments illustrated are described in sufficient detail to enable those skilled in to the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled.

Having disclosed embodiments and the best mode, modifications and variations may be made to the disclosed embodiments while remaining within the scope of the embodiments as defined by the following claims.

Claims

1. An apparatus comprising: a phased locked loop to adjust at least one control parameter of an oscillator to generate a transmitter (Tx) clock signal that is locked to a reference clock signal, where a frequency of the Tx clock signal is a multiple of a frequency of the reference clock signal;a slave delay line including one or more delay buffers configured according to the control parameter to generate a receiver (Rx) clock signal in response to a received clock signal; anda receiver to sample data according to the Rx clock signal.

2. The apparatus of claim 1, further comprising: a clock transmitter to transmit the Tx clock signal; anda data transmitter to transmit data according to the Tx clock signal.

3. The apparatus of claim 1, wherein the oscillator comprises: a delay circuit including one or more delay buffers, where a delay of each buffer is variable and controlled by the control parameter and the delay circuit of the slave delay line is matched to the delay circuit of the voltage controlled oscillator of the PLL.

4. The apparatus of claim 3, wherein the oscillator further comprises: a voltage controlled oscillator (VCO), the phased locked loop to adjust a control voltage of the VCO to adjust a frequency of the Tx clock signal to achieve a phase lock with the reference clock signal.

5. The apparatus of claim 3, wherein the oscillator includes a feedback loop to couple an output buffer to an input buffer of the delay circuit of the oscillator.

6. The apparatus of claim 1, wherein the PLL further comprises: a buffer stage coupled to a delay circuit of the oscillator to enable the PLL to generate a first Tx clock signal and a second Tx clock, wherein a delay between the first Tx clock signal and the second Tx clock signal is selected to enable multi-phase clocking.

7. The apparatus of claim 6, further comprising: at least one phase interpolator coupled to the buffer stage of the slave delay line.

8. The apparatus of claim 7, further comprising: at least one clock tree coupled to the phase interpolator to receive a multi-phase clock; andreceiver data recovery circuit to sample data according to the multi-phase clock.

9. The apparatus of claim 1, further comprising: at least one phase interpolator coupled to the phase locked loop to generate a multi-phase clock in response to a received, multi-phase output from the phase locked loop; andat least one clock tree coupled to the phase interpolator to receive a multi-phase clock.

10. The apparatus of claim 1, wherein the apparatus comprises one of a processor, a memory controller and a serial interface controller.

11. A method comprising: generating a transmitter (Tx) clock signal that is locked to a reference clock according to a control parameter, where a frequency of the Tx clock signal is a multiple of a frequency of the reference clock;configuring at least one slave delay line according to the control parameter;generating, by the slave delay line, a receiver (Rx) clock signal in response to a received clock signal; andsampling data according to the Rx clock signal.

12. The method of claim 11, wherein generating the Tx clock signal comprises: adjusting a control voltage of a voltage-controlled oscillator to lock the Tx clock signal to the reference clock signal; andsetting delay of the slave delay line according to the control voltage, to control a delay of the Rx clock signal to accurately sample data.

13. The method of claim 11, wherein the Tx clock signal is a multi-phase transmit clock signal.

14. The method of claim 11, wherein configuring at least one slave delay line comprises: setting delay buffers of the at least one slave delay line according to a control voltage; andprocessing a received clock signal through the delay buffer of the slave delay line to adjust a phase of the received clock signal relative to incoming data to generate the Rx clock signal.

15. The method of claim 11, wherein sampling data comprises: generating a first Rx clock signal; andgenerating a second Rx clock signal, where a delay between the first Rx clock signal and the second Rx clock signal is controlled by a phase locked loop of a transmitter to enable multi-phase clocking.

16. A system comprising: a dynamic random access memory;a processor;a memory controller coupled between the processor and the memory including a transceiver interface coupled to the processor, the transceiver interface including: a phased locked loop to adjust a control parameter of an oscillator to lock a transmitter (Tx) clock signal with a reference clock signal, where the Tx clock signal is a multiple of the reference clock signal,at least one slave delay line including one or more delay buffers configured according to the control parameter to generate a receiver (Rx) clock signal in response to a received clock signal, anda receiver to sample data according to the Rx clock signal generated by the SDL.

17. The system of claim 16, wherein the processor further comprises: a transceiver interface including: a phased locked loop to adjust a control voltage of a voltage controlled oscillator to lock a processor transmitter (Tx) clock signal with a reference clock signal, where the processor Tx clock signal is a multiple of the reference clock signal;at least one slave delay line including one or more delay buffers configured according to the control voltage to generate a processor receiver (Rx) clock signal in response to the Tx clock signal received from the chipset; anda receiver to sample data according to the Rx clock signal generated by the SDL.

18. The system of claim 16, further comprising: an input/output (I/O) controller coupled to the memory controller and including the transceiver interface.

19. The system of claim 16, wherein the PLL further comprises: a buffer stage coupled to a delay circuit of the oscillator to enable the PLL to generate a first Tx clock signal and a second Tx clock, wherein a delay between the first Tx clock signal and the second Tx clock signal is selected to enable multi-phase clocking.

20. The system of claim 16, wherein the transceiver interface further comprises: at least one phase interpolator coupled to the phase locked loop to generate a multi-phase clock in response to a received, multi-phase output from the phase locked loop;at least one clock tree coupled to the phase interpolator to receive a multi-phase clock; andreceiver data recovery logic to sample data according to the multi-phase clock.