Patent Application
20110060847
The invention relates generally to methods and an apparatus for differential serial communication, and more particularly for interoperating a differential serial communication with a computer graphics display, employing transition minimized differential signaling techniques.
Computer graphics displays typically interface with a graphics coprocessor via a digital visual interface (DVI) link. DVI links typically use transition minimized differential signaling (TMDS) for the base electrical interconnection. These DVI links are used to send pixel data, pixel clock and control signals from a graphics controller to a display device using TMDS. The transition minimization is achieved by implementing an 8b/10b-encoding algorithm. A single-link TMDS interface consists of three data channels and one clock channel. At a higher pixel bandwidth, a dual-link TMDS is employed, with six data channels and one clock channel. The TMDS interface may support a single DVI link at a pixel bandwidth of 1.65 Gbps. However, the TMDS interface faces the challenge of data rates exceeding 1.65 Gbps and the corresponding expense of a high-speed cable with the advent of higher-resolution display panels.
The source data link 14 and the phase-locked loop circuit 18 receive a reference clock signal 30. In response to receiving the reference clock signal 30, the phase-locked loop circuit 18 produces a one-times clock signal 32 and a ten-times clock signal 34 as is known in the art. The source data link 14 provides packet data 36 to the data encoder 16. In response to receiving the packet data 36, the data encoder 16 transmits encoded packet data 38 to the PCI-E transmitter 20. The PCI-E transmitter 20 transmits serialized packet data 40 to the PCI-E receiver 22, as is known in the art.
The phase-locked loop circuit 28 produces different clock phases 42 to the clock recovery circuit 26. The clock recovery circuit 26 provides a recovered clock signal 54 to the data decoder 24. The PCI-E receiver 22 provides received packet data 44 to the data decoder 24. In response to receiving the packet data 44, the data decoder 24 provides decoded packet data 46 to an external I/O bus. The PCI-E transmitter 20 and the PCI-E receiver 22 are adapted to communicate clock recovery information in the packet data 40. For example, the clock recovery circuit 26 may recover the clock information from the packet data 40, as is known is the art.
The PCI-E link architecture 100 replaces the multiple similar parallel busses of the classic PCI bus architecture with PCI-E links with one or more lanes. Each link is individually configurable by adding more lanes so that additional bandwidth may be applied to those links where it is required, for example, in video graphics processing and bus bridges. The basic physical layer consists of dual unidirectional differential links that is implemented as a transmit pair and a receive pair of conductors. The PCI-E link architecture 100 supports a speed of 2.5 gigabits per second per lane per direction. The PCI-E link architecture 100 may support speeds of up to 10 giga transfers/second/direction. A PCI-E link may be linearly scaled by adding multiple lanes. The physical layer supports ×1, ×2, ×4, ×8, ×12 and ×32 lane widths. During initialization, each PCI-E link is configured in response to negotiation of lane widths and frequency of operation by the two agents at each end of the link. Further, during PCI-E initialization, the operating system may discover add-in hardware devices present and then allocate system resources, such as memory, I/O space and interrupts. The PCI-E standard uses an 8b/10b transmission code, identical to that specified in ANSI X3.230-1994. Computer DVI displays typically use DVI-type receivers. However, DVI-type transmitters cannot typically interoperate to drive a PCI-E-receiver.
The present invention is illustrated by way of example and not limitation in the accompanying figures, in which like reference numerals indicate similar elements and in which:
A differential serial communication transmitter control logic receives display configuration control data and in response configures at least one differential serial communication transmitter of a plurality of differential serial communication transmitters in an integrated circuit for communication with a display. For example, the integrated circuit, such as a graphics processor, may include the plurality of differential serial communication transmitters (i.e. PCI-E or other suitably type of transmitter) for communication with a bridge circuit and a display (i.e. DVI or other suitable interface) within a computer system. The differential serial communication transmitter control logic may configure at least one of the plurality of PCI-E transmitters for communication with the DVI display via a differential serial communication display link (i.e. DVI or other suitable interface). The plurality of PCI-E transmitters may also be configured for communication with one or more other bridge circuits, such as a northbridge.
Among other advantages, an integrated circuit, such as a graphics processor, includes a plurality of configurable differential serial communication transmitters for communication with any suitable external device, such as a graphics display, or a bridge circuit, such as a northbridge. As a result, the integrated circuit may be manufactured using a single type of configurable differential serial communication transmitter, such as PCI-E transmitters, rather than different types of differential serial communication transmitters, such as both PCI-E transmitters and TMDS transmitters. According to this embodiment, for example, since only a single type of differential serial communication transmitter is used to interoperate with the PCI-E bus and DVI interface, fewer differential serial communication transmitters are required to be allocated on the integrated circuit, thus saving valuable space and reducing the number of transistors used on the integrated circuit.
Further, since the plurality of differential serial communication transmitters may be configured for communication with a suitable device, fewer pins on the integrated circuit are required. In the situations where TMDS transmitters are required external to the integrated circuit, such external DVI-type transmitters and special pin allocations are no longer necessarily required. Additionally, since a single type of differential serial communication transmitter is utilized on the integrated circuit, different types of differential serial communication transmitters are not required. Yet another advantage may be realized by essentially standardizing the plurality of differential serial communication transmitters on an integrated circuit, so that, as improvements in data transfer rates and features that are developed for these standard interfaces, improvements to the differential serial communication transmitters on the integrated circuit are more readily implemented.
The differential serial communication transmitter control logic 210 may be one or more suitably programmed processors, such as a microprocessor, a microcontroller or a digital signal processor and, therefore, includes associated memory such as memory (312 and 314 shown in
The various elements of the differential serial communication transmitter configuration circuit 200 are linked by a plurality of links. The links may be any suitable mechanisms for conveying electrical signals or data, as appropriate. According to one embodiment, the interface between the differential serial communication display (i.e. TMDS) transmitter 242, the differential serial communication bridge transmitter 244, the differential serial communication transmitter control logic 210 and the differential serial communication display (i.e. TMDS) receiver 246 may be a host processor to graphics coprocessor interface, such as a PCI bus, an AGP bus, a PCI-E bus, an I2C (IC to IC) bus or any other suitable type of bus, either standardized or proprietary. Alternatively, theses interfaces may be integrated circuit interconnections within an application-specific integrated circuit (ASIC).
The integrated circuit 220 is shown to include a coprocessor 318, which includes the plurality of differential serial communication (i.e. PCI-E) transmitters 240 (allocated between the differential serial communication display (i.e. TMDS) transmitter 242, and the differential serial communication bridge transmitter 244), as well as at least one differential serial communication bridge receiver 320.
The coprocessor 318 includes a plurality of differential serial communication transmitters 240, which includes, for example, the requisite differential transmit-and-receive drivers, compliant, for example, with the PCI-E specification, or any other suitable differential serial communication link. The graphics controller 330, provides graphics packet data 332 and control data 334 to the differential serial communication display (i.e. TMDS) transmitter 242. The coprocessor 318 may be a graphics coprocessor or any suitable graphics processor, including but not limited to the types sold and manufactured by ATI Technologies, Inc. of Thornhill, Ontario, Canada.
The bridge circuit 310 includes at least a differential serial communication bridge receiver 340 and a differential serial communication bridge transmitter 342. The bridge circuit 310 may be a northbridge or any suitable circuit as known in the art. The bridge circuit 310 may be suitably connected to the memory 314, configuration memory 312, processor 316 and coprocessor 318 through a suitable bus, such as a PCI-E bus or any bus suitable to other peripheral components. In addition, bridge circuit 310 and coprocessor 318 may also have a plurality of differential serial communication links, including one-way or bi-directional links coupled to other peripheral devices.
The memory 314 and the configuration memory 312 may be, for example, random access (RAM), read-only memory (ROM), optical memory or any suitable storage medium located locally or remotely, such as via a server or distributed memory, if desired. Additionally, the memory 314 and configuration memory 312 may be accessible by a wireless base station, switching system or any suitable network element via the Internet, a wide area network (WAN), a local area network (LAN), a wireless wide access network (WWAN), a wireless local area network (WLAN), such as but not limited to an IEEE 802.11 wireless network, a Bluetooth® network, an infrared communication network, a satellite communication network or any suitable communication interface or network. Memory 314 may be part of system memory, graphics memory, or any other suitable memory.
According to one embodiment, the differential serial communication transmitter configuration system 300 may be part of a computer system or other processor-based system. The computer system or other processor-based system may include a central processing unit, such as a processor 316, a coprocessor 318, such as the graphics video coprocessor, memory 314, such as system memory, configuration memory 312, such as BIOS memory, bridge circuit 310, such as a northbridge, and display 230. In such systems, the processor 316 functions as a loosely coupled coprocessor. By way of example, the coprocessor 318 may be an integrated circuit on a single semiconductor die, such as an application-specific integrated circuit (ASIC). Additionally, the coprocessor 318 may include memory (not shown), such as but not limited to dynamic random access memory (DRAM). This memory may reside on the same semiconductor die (e.g., ASIC) as the coprocessor 318 or it may be separate and connected through board-level or package-level traces.
The differential serial communication transmitter configuration system 300 is shown as a computing system, which may be, for example, incorporated in a hand-held device, laptop computer, desktop computer, server, or any other suitable device. The processor 316 may be one or more suitably programmed processors, such as a microprocessor, a microcontroller or a digital signal processor, and therefore includes associated memory, such as memory 314 and configuration memory 312, that contains executed instructions that, when executed, cause the differential serial communication transmitter control logic 210 to carry out the operations described herein.
According to the embodiment shown in
In the embodiment shown in
As shown in steps 510 and 520, the differential serial communication transmitter control logic 210 receives the display configuration control data 260 and, in response, configures at least one differential serial communication transmitter of the plurality of differential serial communication (i.e. PCI-E) transmitters 240 as differential serial communication display (i.e. TMDS) transmitter 242, for communication with the display (i.e. DVI) 230 via the differential serial communication display (i.e. DVI) link 248. As previously described, each of the plurality of differential serial communication transmitters (i.e. PCI-E) 240 are operably configurable to communicate with another differential serial communication link, such as the differential serial communication bridge link (i.e. PCI-E) 250.
According to one embodiment, such as, the embodiment shown in
According to one embodiment the differential serial communication transmitter control logic 210 configures the differential serial communication display (i.e. TMDS) transmitter 242, the transmitter zero circuit 412, transmitter one circuit 414, transmitter two circuit 416 and transmitter three circuit 418 to form the data lane zero 438, the data lane one 440, the data lane two 442 and the clock lane 444, respectively.
Alternatively, the differential serial communication display (i.e. TMDS) transmitter 242 may be configured with six transmitter circuits to provide six data lanes, or any other suitable number of transmitter circuits as required by the differential serial communication display receiver 246, within display 230. According to one embodiment, the differential serial communication display receiver 246 is a DVI-compliant receiver. The number of desired lanes may be determined by the differential serial communication transmitter control logic 210 operating as a driver executing on the processor 316. For example, the display configuration control data 260 stored in the configuration memory 312 may indicate the type of display (i.e. DVI) 230 in the computer system and may also indicate the number of receiver circuits, such as receiver zero circuit 430, receiver one circuit 432 and receiver two circuit 434, within the differential serial communication display (i.e. TMDS) receiver 246. In one embodiment, a link width command register and link width control register are integrated within the coprocessor 318 to set the link to the proper width size. Such command can be executed during initiation, a conventional reset or power-on condition.
The data encoder 410 includes a PCI-E/DVI selector data input register 606, a scrambler circuit 608, a packet multiplexor 610, and a data encoder 612. The transmitter circuit 602 includes a parallel to serial converter 614, a current drive register 616, at least one driver(s) 618, a receiver detect circuit 620 and a common mode circuit 622. The parallel to serial converter 614 further includes a serializer 624 and a serial multiplexor 626. The at least one driver/driver(s) 618 further includes a main driver 628 and an enhancement driver 630. The clock circuit 420 includes a phase-locked loop circuit 632, a phase-locked loop clock bandwidth and clock mode configuration data register 634, a ten-times multiplier 636, a clock multiplexor 638 and a clock driver 640.
As shown in step 730, the clock multiplexor 638 receives the reference clock signal 422. In response to the phase-locked loop clock bandwidth and clock mode control information 262, the clock multiplexor 638 selects either the one-time clock signal 642 from the output of the phase-locked loop clock circuit 632 or the (one-time) reference clock signal 422. As understood by one skilled in the art, the selection of the clock signal 646 based on the output of the clock phase-locked loop circuit 632, which produces the one-time clock signal 642 used in the data encoder 410 and the transmitter 602, will cause the phase of the differential clock signal 648 and the differential serial data 650 to be in phase. In contrast, if the clock multiplexor 638 generates the clock signal 646 based on the (one-time) reference clock signal 422, then the differential clock signal 648 and the differential serial data 650 will not be in phase. Depending on clock mode configuration required by the differential serial communication display (ie. TMDS) receiver 246, the clock multiplexor 638 generates the clock signal accordingly. Clock driver 640, in response to receiving the clock signal 646, generates a differential clock signal 648.
As shown in step 740, PCI-E/DVI data input register 606 receives the PCI-E/DVI input data 266 from the processor 316, and in response provides the PCI-E/DVI input selector data 266 to the packet multiplexor 610. In response to receiving the PCI-E/DVI input selector data 266, the packet multiplexor 610 selects either the graphics data packets 332 and control data 334 from the graphics control 330 or data packet 652 from the scrambler 608. For example, when the differential serial communication (i.e. PCI-E) transmitter is configured to communicate with the bridge circuit 310, the PCI-E/DVI input selector data 266 may cause the packet multiplexor 610 to produce selected data packets 654 based on the data packet 652. However, if the differential serial communication (i.e. PCI-E) transmitter is configured to communicate with the differential serial communication display (i.e. TMDS) receiver 246, then the PCI-E/DVI input selector data 266 may cause the packet multiplexor 610 to generate the selected data packets 654 based on the graphics data packets 632 and the control data 334.
As shown in step 750, in response to receiving the drive current control data 264 from processor 316, the current driver register 616 provides the drive current control data 264 to at least one driver 618, including the main driver 628 and the enhancement driver 630. For example, when the driver(s) 618 are coupled to the differential serial communication display (i.e. TMDS) receiver 246 via the differential serial communication display (i.e. DVI) 248, the driver current control data 264 may indicate the driver current required by the driver 618 to provide sufficient drive current to the differential serial communication display (i.e. TMDS) receiver 246. Accordingly, the processor 316 varies the drive current control data 264 to correspond with a current load in the differential serial communication display (i.e. TMDS) receiver 246. According to one embodiment, the drive current control data 264 controls the main driver 628 and/or the enhancement driver 630 in order to provide pre-emphasis to develop a low-voltage differential signal as is known in the art.
As understood by one skilled in the art, a data gate 660 receives the ten-times clock signal 644 and the serial data 646, and in response provides gated serial data 648 to the enhancement driver 630. Accordingly, the data gate 660 may gate the serial data 646 so that the enhancement driver 630 provides enhanced current output driving capabilities synchronous with the serial data 646, in order to provide enhanced current drive capabilities
Among other advantages, the integrated circuit 220, such as a graphics processor, includes a plurality of configurable differential serial communication transmitters 240 for communication with any suitable external device, such as a DVI graphics display 230 or the bridge circuit 310, such as a northbridge. As a result, the integrated circuit 220 may be manufactured using a single type of configurable differential serial communication transmitter, such as PCI-E transmitters, rather than different types of differential serial communication transmitters, such as both PCI-E transmitters and TMDS transmitters. Accordingly, since only a single type of differential serial communication transmitter may be used in the integrated circuit 220, fewer differential serial communication transmitters are required to be allocated on the integrated circuit 220, thus saving valuable space and reducing the number of transistors used on the integrated circuit.
Further, since the plurality of differential serial communication (i.e. PCI-E) transmitters 240 may be configured for communication with any suitable device, fewer pins on the integrated circuit 220 are required, since a different type of differential serial communication transmitter is not required. Therefore, special pin allocations on the integrated circuit 220 for multiple types of differential serial communication transmitters are not required. Further, in the situations where external TMDS transmitters are required external to the integrated circuit 220, such external DVI-type transmitters, are no longer necessarily mounted externally to the integrated circuit 220, as may be the case. Additionally, since a single type of differential serial communication transmitter is utilized on the integrated circuit 220, different types of differential serial communication transmitters are not required. Yet another advantage may be realized by essentially standardizing the plurality of differential serial communication transmitters on the integrated circuit so that, as improvements in data transfer rates and features that are developed for these standard type interfaces, improvements to plurality of the differential serial communication transmitters 240 on the integrated circuit 220 are more readily implemented.
It is understood that the implementation of other variations and modifications of the present invention and its various aspects will be apparent to those of ordinary skill in the art and that the invention is not limited by the specific embodiments described. It is therefore contemplated to cover by the present invention any and all modifications, variations or equivalents that fall within the spirit and scope of the basic underlying principles disclosed and claimed herein.
This application is a divisional application of U.S. application Ser. No. 11/004,201 filed on Dec. 2, 2004, entitled “METHOD AND APPARATUS FOR TRANSPORTING AND INTEROPERATING TRANSITION MINIMIZED DIFFERENTIAL SIGNALING OVER DIFFERENTIAL SERIAL COMMUNICATION TRANSMITTERS”, having inventors Nancy Chan et al., owned by instant Assignee and is incorporated herein by reference and is related to application having docket number 00100.16.0030, filed on even date, entitled “METHOD AND APPARATUS FOR TRANSPORTING AND INTEROPERATING TRANSITION MINIMIZED DIFFERENTIAL SIGNALING OVER DIFFERENTIAL SERIAL COMMUNICATION TRANSMITTERS”, having inventors Nancy Chan et al., owned by instant Assignee and is incorporated herein by reference which is a continuation application of U.S. application Ser. No. 11/004,201 filed on Dec. 2, 2004, entitled “METHOD AND APPARATUS FOR TRANSPORTING AND INTEROPERATING TRANSITION MINIMIZED DIFFERENTIAL SIGNALING OVER DIFFERENTIAL SERIAL COMMUNICATION TRANSMITTERS”, having inventors Nancy Chan et al., owned by instant Assignee and is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11004201 | Dec 2004 | US |
| Child | 12944501 | US |
