KR100433873B1 - Method And Apparatus for realizing Hot Plug Detection by using Digital Visual Interface - Google Patents

Abstract

The present invention relates to a method for implementing Hot Plug Detection (HPD) and a device thereof, and to provide a method for smoothly implementing HPD using DVI, thereby reducing the system load between a host device and a display device connected via DVI. have.

In order to achieve the above object, according to the present invention, the host device receives the EDID from the display device through the DDC communication protocol according to the HPD signal, parses it, extracts the corresponding product packet identifier through the parsed EDID, and extracts the corresponding product packet. After determining whether the HPD signal is changed by storing the identifier, and extracting the corresponding product packet identifier of the changed HPD signal according to the determination result, if the extracted product packet identifier is not the same as the stored product packet identifier, the stored product packet identifier is refreshed. A step and apparatus for updating with the extracted product packet identifier are required.

Description

Method for implementing HPD between devices connected by digital interface and device therefor {Method And Apparatus for realizing Hot Plug Detection by using Digital Visual Interface}

The present invention relates to a method and apparatus for implementing Hot Plug Detection (HPD) using a digital visual interface (DVI).

The digital visual interface (DVI) refers to a digital interface between a host device such as a computer and a set-top box, and a display device such as a monitor and a digital television. There are generally three types of Plug and Play (PnP), DFP, and DVI methods.

PnP is a standard adopted by the Video Electronic Standards Association (VESA) in 1997. It is a transmission protocol interface that adopts TMDS (Transmission Minimized Differential Signal), also called panel link, as a transmission protocol. Just plug it in, plug it in, and your computer will automatically reconfigure your environment for optimal use.

The above PnP is also applied to the monitor. For this purpose, the PnP monitor should be able to provide the computer with information on the optimal available modes and various adjustment states, as well as the function of receiving and displaying signals from the computer. .

That is, when the PnP monitor and the computer are connected and operated with a signal cable, various information is transmitted from the monitor to the computer, and the computer automatically selects an optimal mode suitable for use based on the information. It will provide the best screen for users.

These PnP-enabled digital connectors can transmit both analog and digital, but to do so, they are priced higher by incorporating a solution that integrates Universal Serial Bus (USB) and IEEE1394 / Firewire signals. The lack of interest in costly connectors eventually made it the standard for digital interfaces.

So in the Compaq-led DFP (Digital Flat Panel), the PnP method and functionality are almost the same, but costly special features such as analog signals, USB and IEEE1394 have been left out to reduce the price.

However, the DFP method also has a drawback that the maximum resolution is limited to SXGA (1280 × 1024), and it cannot be adopted in graphic boards and analog monitors that transmit existing digital signals by transmitting only digital signals.

In order to make up for these drawbacks, it is recently attracting the most attention as a Video Graphics Array (VGA) interface, and the marketability is expected to come up with a DVI (Digital Visual Interface) method.

DVI was proposed by the Digital Display Working Group (DDWG), which includes many DFP-related companies, and it is compatible with existing digital interface methods by using TMDS protocols such as PnP and DFP. In case of PnP or DFP with only a link of, the maximum resolution is limited to 1280 × 1024, but DVI can double the maximum pixel rate by having two links, and also analog signal in addition to digital signal in terms of signal transmission It can also be connected to existing analog monitors, so this type of DVI is expected to become the standard for digital interfaces in the future.

In particular, in recent years, several manufacturers are moving to apply such DVI as an interface standard between digital video / audio devices, such as set-top boxes, digital television receivers or digital video displays. The trend is to use it as a digital connection standard for digital television receivers.

Meanwhile, DVI provides various functions as well as a digital interface, one of which is a Hot Plug Detect (HPD) function, which means that a display device informs a host device of its own presence.

Hereinafter, a conventional method of implementing HPD will be described.

First, in order to implement the HPD function, a display data channel (DDC), which is a protocol for storing EDID (Extended Display Identification Data), which is its own information, and transmitting it to a host device, must be defined.

Generally, the host device supports the resolution of the display device used by the host device, and does not have information about the resolution that is appropriate for the software currently being used.

However, if the DDC is supported, the display device sends its information to the host device, and the host device receives this information and automatically displays the optimal screen within the range supported by the display device no matter what software the user uses. give.

In order to standardize the DDC protocol, the Video Electronic Standards Association (VESA), a non-profit corporation formed between US computer and peripheral companies, has established a standard for DDC (Display Data Channel) transmission.

According to the enacted standard, DDC-supported display devices include one-way that provides EDID information to the host device and two-way that can provide information to the display device from the host device.

For example, "DDC1 is a one-way transmission method that provides display information to a host device as the most basic communication method, and the host device cannot control the information transmission.

When such a display device is connected to a host device and the display device is powered on, the display device provides information to the host device using the vertical frequency as a transmission clock, and the host device displays the display device in a mode that matches the information provided from the display device. To provide the best possible signal.

In addition, DDC2B is a bidirectional transmission method for communication between display device and host device, based on I2C protocol. It has the feature of using an access bus.

The table below shows the comparison with the conventional analog VGA connection.

PIN number VGA DDC1,2 Disp DDC-1 Host DDC2 Host One R R R R 2 G G G G 3 B B B B 4 ID bit 2 optional ID bit 2 ID bit 2 5 Test return return return 6 R return R return R return R return 7 G return G return G return G return 8 B return B return B return B return 9 NC + 5V load + 5V supply + 5V supply 10 Sync return Sync return Sync return Sync return 11 ID bit 0 optional ID bit 0 ID bit 0 12 ID bit 1 SDA Data SDA 13 H. syc H. syc H, syc H. syc 14 V. syc V. syc V. syc V. syc 15 ID bit 3 SCL ID bit 3 SCL

As shown in Table 1, the + 5V provided by the host device is connected through pin 9 in the case of DDC in the 15-pin deserver connector, and from the display device through pin 12 in synchronization with the vertical synchronization clock of pin 14 in DDC1. Data is transferred to the host device, and in DDC2, data can be transmitted in both directions through pins 12 and 15.

The host device with the DDC-1 function reads the DDC data sent from the display device, and if there is no data, the host device recognizes the old display device and does not send + 5V power to pin 9, but whether the old display device or the power is turned on. I don't recognize the difference.

The host device with the DDC2AB function first contacts the access bus, finds the EDID if there is no response, and then considers the old display device if there is no response.

The host device having the DDC2B function checks the EDID (Extended Display Identification) using the DDC2B. If there is no response, the host device is regarded as an old display device and gives up the DDC2B function. An analog HPD implementation method will be described with reference to FIG. 1.

1 is a signal flow diagram illustrating a conventional analog HPD implementation method.

As shown in FIG. 1, a microcomputer built in a computer (host device) first checks the presence or absence of EDID information through a DDC2B (S100). The EDID information is continuously circulated as long as a vertical synchronization signal is input through a VGA cable. It can be checked periodically because it is transmitted.

If it is determined that the EDID information exists (S110), the microcomputer determines that the monitor (display device) corresponding to the EDID is connected (S120). Otherwise, the return data is monitored through the VGA cable. The return data is a kind of call data for calling the monitor information.

Then, the response data of the transmitted return data is judged (S111). If the response data transmitted through the VGA cable is a null message, the existing monitor is regarded as an old monitor and the new monitor is determined to be connected. In contrast, when the retransmission data of the transmitted return data is not a null message (S112), an operation of periodically checking the EDID is performed through the DDC2B (S100).

This analog HPD implementation method, as described above, the computer periodically checks the presence of EDID to implement HPD, if the EDID does not exist for reasons such as poor connection or power off The return data is transmitted to the monitor, and it is determined whether the response data of the transmitted return data is a null message, and accordingly, the EDID is checked again to implement HPD.

However, the HPD implementation method using the conventional VGA cable increases the system load in the communication system between the computer and the monitor, which causes the computer to take a considerable time to format a video data structure that conforms to the monitor's display standard. there was.

Accordingly, the present invention is to solve the conventional problems as described above, to reduce the system load of the display device and the host device, to implement the HPD using DVI to quickly format the video data structure conforming to the display standard Its purpose is to provide a method and a system thereof.

HPD implementation method using the DVI of the present invention for achieving the above object, the host device detects the HPD signal, and the host device receives the EDID from the display device through the DDC communication protocol according to the detected HPD signal And parsing the received EDID, extracting the corresponding product packet identifier through the parsed EDID, storing the extracted corresponding product packet identifier, and maintaining the state of storing the presence or absence of the change of the HPD signal. Determining whether the HPD signal has changed, extracting the corresponding product packet identifier of the HPD signal, determining whether the extracted product packet identifier is identical to the stored product packet identifier, and determining If the result is not identical, the stored product packet identifier is updated with the extracted product packet identifier. Characterized by comprising the steps:

In addition, the HPD implementation device between the devices connected via the digital interface of the present invention, a DVI decoder for decoding the HPD signal received from the display device by the host device, the HPD signal decoded through the DVI decoder and periodically the change state Whether or not the HPD detection unit to detect, the memory for storing the corresponding product packet identifier of the HPD signal detected by the HPD detection unit, the product packet identifier stored in the memory and the product packet identifier of the new HPD signal whose state has changed And a host microcomputer for determining and updating the product packet identifier stored in the memory according to the determination result.

1 is a signal flow diagram illustrating a conventional analog HPD implementation method,

2 is a signal flow diagram illustrating a method of implementing HPD using DVI according to the present invention;

3 is a conceptual diagram illustrating a logical communication protocol of DVI applied to the present invention,

4 is a diagram illustrating a connection between a host device and a display device according to the present invention;

5 is a block diagram illustrating a system configuration of a host device and a display device according to the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

First, in order to facilitate understanding of the present invention, a brief description will be given of DVI supporting general HPD function.

The physical PIN assignment format of DVI, which is a conventional digital connection standard, is shown in Table 2.

PIN Signal assignment PIN Signal assignment PIN Signal assignment One TMDS DATA2- 9 TMDS DATA1- 17 TMDS DATA0- 2 TMDS DATA2 + 10 TMDS DATA1 + 18 TMDS DATA0 + 3 TMDS DATA24shield 11 TMDS DATA1 / 3shield 19 TMDS DATA0 / 5shield 4 TMDS DATA4- 12 TMDS DATA3- 20 TMDS DATA5- 5 TMDS DATA4 + 13 TMDS DATA3 + 21 TMDS DATA5 + 6 DDC Clock 14 + 5V Power 22 TMDS clock shield 7 DDC Data 15 Ground (FOR + 5V) 23 TMDS clock + 8 No connect 16 Hot Plug Detect 24 TMDS chock-

Table 2 above is a PIN assignment format for connecting only digital signals, and five more pins are required for connecting analog signals, and these five pins and eight pins respectively have analog RGB signals, horizontal sync signals, and vertical sync. The signal is assigned so that the analog signal can be connected.

The TMDS is a panel link, and Hot Plug Detection (HPD), DDC DATA, DDC CLOCK, + 5V POWER and GROUND are control signals (CTL).

The logical transmission protocol of the TMDS and control signals constituting Table 2 is shown in FIG. 3.

As shown in FIG. 3, pixel data and control signals digitally converted in a host device such as a computer or a set top box are transmitted to a TMDS transmitter in synchronization with a clock signal and then supported by the DDC protocol through an encoding process. The channel is transmitted to a TMDS receiver of a display device such as a monitor or a digital television, and the TMDS receiver decodes the transmitted pixel data and is displayed under the control of a controller.

In addition, DVI provides various functions as well as an interface of digital signals, one of which is Hot Plug Detection (HPD).

The HPD refers to a function in which the display device notifies its presence to a host device to which the display device is connected. For example, when the display device applies a high level potential of + 2.4V through a corresponding hardware pin that performs HPD, After receiving the signal, the host device receives the EDID of the display device through the DDC protocol and recognizes the information of the display device. The EDID is information transmitted from the display device to the host device, for example, a manufacturer. It refers to data composed of a manufacturer ID indicating a, a manufacturing ID indicating a model name of a product, whether a power saving mode function of a display device is supported, and timing information.

This EDID is a data format having 128 bytes of information as shown in Table 3.

Byte size division 8 bytes Header 10 bytes Manufacturer / Product Identifier 2 bytes EDID format version 15 bytes Basic Display Parameters / Features 19 bytes Extended / Standard Timing 72 bytes Timing and Monitor Details 1 byte Extension flag 1 byte Whitsum Sum 128 bytes

The EDID includes manufacturer / product information, parameter information, timing information, and the like as shown in Table 3, so that the host device can automatically set the mode.

In the HPD implementation method using DVI according to the present invention, as shown in FIG. 2, a host device 200 detects an HPD signal (S200).

Then, in step 210, the host device receives an EDID from the display device through the DDC communication protocol and parses it according to the HPD signal detected through the 200 th step S200.

In operation 220, the corresponding product packet identifier (Vendor / Product Identifier) of 10 bytes included in the parsed EDID is extracted and stored.

Next, step 230 (S230) is a step of determining whether there is a change in the HPD signal while maintaining the state of storing through the 220 step (S220), that is, the power of the display device when data is transmitted between the display device and the host device. It is a step of periodically checking the HPD signal whose signal level is changed according to the change of state or the change of DVI connection state.

If it is determined that the HPD signal has not been changed through the 230 th step S230, the process proceeds to the 200 th step S200 of detecting the HPD signal. If it is determined that the HPD signal has changed, the 240 th step is determined. Step S240 and step 250 are performed in order.

The 240th step (S240) is to parse the EDID received by receiving the EDID of the changed HPD signal, the 250th step (S250) is the corresponding product from the EDID parsed through the 240th step (S240) Extracting the packet identifier.

Next, it is determined whether the extracted product packet identifier and the stored product packet identifier are identical in operation 250 (S250).

If the two product packet identifiers are not determined to be the same through the step 260 (S260), the stored product packet identifier is updated with the product packet identifier extracted through the step 250 (S250). In step 230, if the two product packet identifiers are determined to be the same, the stored product packet identifiers are kept intact and periodically checked whether the level of the HPD signal changes. Proceed to S230).

Meanwhile, as shown in FIG. 5, an apparatus for implementing HPD between devices connected through the digital interface of the present invention includes a DVI decoder unit for decoding a HPD signal received from the display device by a host device, and an HPD decoded through the DVI decoder unit. HPD detection unit for periodically detecting the signal and the change state, a memory for storing the corresponding product packet identifier of the HPD signal detected by the HPD detection unit, a product packet identifier stored in the memory and a new HPD signal with the changed state It is determined that the identity of the product packet identifier of the host microcomputer to update the product packet identifier stored in the memory according to the determination result.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

4 is a DVI connection diagram in which a host device and a display device are connected by DVI, and FIG. 5 is a configuration block diagram.

First, as shown in FIG. 5, the HPD signal encoded through the DVI encoder unit 51 passes through the interface units 53 and 44 to the DVI decoder unit 41 of the host device under the control of the display microcomputer 52. When transmitted, the DVI decoder 41 decodes the encoded HPD signal and outputs the encoded HPD signal to the HPD detector 42.

Then, when the HPD detection unit 42 detects the decoded HPD signal and outputs the detected HPD signal to the host microcomputer 43, the host microcomputer 43 receives the EDID containing its information from the display device according to the HPD signal. Is transmitted through the interface unit 44 or 53. The EDID is stored in the memory 54 of the display device, and the display micom 52 stores the EDID at the request of the host device that detects the HPD signal. The load is transmitted to the host device through the interface unit 44 or 53.

Next, the host microcomputer 43 parses the EDID transmitted to the host device as described above, extracts the product packet identifier of 10 bytes included in the EDID, and temporarily stores the extracted product packet identifier in the memory 44.

Then, in this state, the level of the detected HPD signal is changed according to a change in power state of the display device or a DVI connection state, and the changed information is detected by the HPD detection unit 42 and the host signal is detected by the host microcomputer. When outputting to 43, the host microcomputer 43 receives and parses the corresponding EDID of the changed HPD signal, extracts the product packet identifier of the changed HPD signal, and extracts the same product packet identifier from the stored product packet identifier. Judge

If the two product packet identifiers are the same as the result of the determination, the stored product packet identifier is kept as it is. Otherwise, if the two product packet identifiers are not the same, the product packet identifier stored in the memory 44 is converted to the corresponding product of the converted HPD signal. Update with a packet identifier.

As described in detail above, a method and apparatus for implementing HPD using DVI according to the present invention, when the HPD signal level is changed, does not perform a full analog flow method for a new HPD, and changes the product packet identifier of the HPD signal. By implementing a method of determining only the identity of the stored product packet identifier, the system load generated during the implementation of the host device and the display device may be reduced. Accordingly, the host device may quickly format a video data structure that conforms to the display standard. It has the effect of making it possible.

Although the invention has been described in detail only with respect to the specific examples described, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (7)

A first step of detecting a Hot Plug Detection (HPD) signal from a display device connected via a DVI (Digital Visual Interface); A second step of receiving and parsing extended display identification data (EDID) from the display device through a display data channel (DDC) communication protocol according to the detection of the HPD signal of the first step; Extracting and storing a predetermined product packet identifier for identifying a display device connected by DVI from a result of parsing the EDID in the second step; A fourth step of waiting and determining whether or not the HPD signal transmitted from the display device is changed through the DVI by using a predetermined HPD detection device separately provided in the host device while maintaining the storage state of the third step; As a result of the determination in the fourth step, if it is determined that the HPD signal is changed, the corresponding product packet identifier is extracted from the display device which transmits the changed HPD signal to determine whether or not the identity with the product packet identifier stored in the third step is determined. The fifth step; If it is determined that the two product packet identifiers are not the same as the determination result of the fifth step, the product packet identifier stored in the third step is updated with the product packet identifier extracted through the fifth step. HPD implementation method between the devices connected by a digital interface, characterized in that made. The method of claim 1, wherein the EDID information is; HPD implementation method between the devices connected by the digital interface, characterized in that transmitted from the display device connected via the interface. The method of claim 1, wherein the fourth step comprises: If it is determined that the HPD signal has not changed, the first step of detecting the HPD signal, characterized in that the HPD implementation method between devices connected via a digital interface. The method of claim 1, wherein the extracting of the corresponding product packet identifier of the HPD signal of the fifth step comprises: And receiving and parsing the corresponding EDID of the changed HPD signal, and extracting the corresponding product packet identifier through the parsed EDID. The method of claim 1, wherein the fifth step comprises: If it is determined that the extracted product packet identifier and the stored product packet identifier are the same, the fourth step of determining whether there is a change in the HPD signal is performed. A DVI decoder to decode the HPD signal received from the display device; An HPD detection unit periodically detecting the HPD signal decoded through the DVI decoder and its change state; A memory for storing a corresponding product packet identifier of the HPD signal detected by the HPD detection unit; And a host micom configured to determine whether or not the product packet identifier stored in the memory and the product packet identifier of the new HPD signal whose state has changed and update the product packet identifier stored in the memory according to the determination result. HPD implementation device between devices connected by an interface. The method of claim 6, wherein the microcomputer is; If the two product packet identifiers are not the same, the product packet identifier stored in the memory is updated with the product packet identifier of the new HPD signal whose state has changed, and if the two product packet identifiers are the same, maintaining the product packet identifier stored in the memory as it is. A device for implementing HPD between devices connected by a digital interface.