Video monitor multiplexing circuit

• US 6,600,747 B1
• Filed: 09/17/1998
• Issued: 07/29/2003
• Est. Priority Date: 09/17/1998
• Status: Expired due to Term

• Current Assignee: Dell Products LP (Dell Technologies Inc.)
• Original Assignee: Dell Products LP (Dell Technologies Inc.)
• Inventors: Sauber, William F.
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): Tran, Thien D
• Application Number:
  US09/156,085
• Time in Patent Office: 1,776 Days
• Field of Search: 370/532, 370/537, 370/395.1, 370/395.64, 370/465, 370/466, 370/539, 345/707, 345/761, 345/180, 345/11
• US Class Current: 370/395.64
• CPC Class Codes: G09G 2370/047 using display data channel standard [DDC] communication
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04

Abstract

A single group of signals interfaces a computer system to either an analog display or a digital display. A video signal in digital format and a video signal in analog format are both supplied to a circuit that multiplexes the digital signal and the analog signal, generating an appropriate output signal for the display, either analog or digital, that is coupled to the computer system. In one example, the signal connector interfaces the computer system to either an analog CRT display or a digital FPD display. The multiplexer multiplexes the analog signal and the digital signal supplied by the computer system and generates an output signal that is suitable for the CRT display or the FPD display, depending on the type of display coupled to the computer system.

Claims

1. An apparatus comprising:

a video controller operable to generate at least two video signals, the at least two video signals including an analog video signal and a digital video signal;

a connector operable to provide a plurality of pins for attaching a video monitor thereto, the connector operable to receive a monitor identification information from the video monitor on at least one of the pins;

a circuit coupled to the video controller and coupled to the connector, the circuit operable to receive the at least two video signals from the video controller and the monitor identification information from the connector; and

the circuit operable to use the monitor identification information to selectively couple one of the at least two video signals to the connector.

3. The apparatus of claim 1 wherein the video monitor is selected from a group comprising:

a DDC monitor;

a DDC compatible monitor; and

a monitor compatible for use with a DDC emulator.

4. The apparatus of claim 1 wherein the video controller comprises:

a digital to analog converter;

a memory;

an imaging circuit; and

a display refresh circuit.

2. An apparatus comprising:

a video controller operable to generate at least two video signals, the at least two video signals including an analog video signal and a digital video signal;

a connector operable to provide a plurality of pins for attaching a video monitor thereto;

a circuit coupled to the video controller and coupled to the connector, the circuit operable to receive the at least two video signals from the video controller, wherein the circuit selectively couples one of the at least two video signals to the connector based on the electrical signal of at least one of the connector pins;

one of a multiplexer coupled between the video controller and the connector and a multiplexer incorporated into the video controller and electrically coupled to the connector, the multiplexer comprising;

select lines for selecting one of digital signal data lines, analog signal data lines, and null lines; and

a plurality of switches; and

one of a digital to differential circuit coupled between the video controller and the multiplexer and a digital to differential circuit incorporated into the video controller and electrically coupled to the multiplexer.

5. An apparatus comprising:

a switch;

a first input terminal coupled to the switch for receiving an analog signal;

a second input terminal coupled to the switch for receiving a differential digital signal;

an output terminal coupled to the switch, the switch for multiplexing the analog signal and the differential digital signal, and the output terminal for supplying a multiplexed signal to a video monitor; and

a video controller communicatively coupled to the switch, the video controller operable to receive monitor identification information from the video monitor to control whether the analog signal or the differential digital signal is supplied as the multiplexed signal.

6. The apparatus of claim 5 further comprising a multiplexer having a select line coupled to a general purpose input/output line.

7. The apparatus of claim 5 further comprising a multiplexer having a select line coupled to the video controller.

8. The apparatus of claim 7 further comprising:

a digital to differential circuit that receives a digital video signal from the video controller and outputs the differential digital signal to the multiplexer.

9. The apparatus of claim 7 further comprising:

a digital to analog converter that receives a digital video signal from the video controller and sends an analog video signal to the multiplexer.

10. The apparatus of claim 7 wherein the multiplexer is connected to a connector coupled between the video monitor and the multiplexer.

11. The apparatus of claim 10 wherein the video monitor is selected from a group comprising:

a digital video monitor; and

an analog video monitor.

12. The apparatus of claim 11 wherein the video monitor is a Display Data Channel (DDC) monitor including a DDC clock line and a DDC data line.

13. The apparatus of claim 12 wherein the DDC clock line and the DDC data line are coupled to the video controller.

14. The apparatus of claim 13 wherein the video controller reads the DDC data line in the format of Extended Display Identification Data (EDID), and outputs one of an electrical signal indicating a digital code to the apparatus as the select line and an electrical signal indicating an analog code to the apparatus as the select line.

15. The apparatus of claim 11 wherein the select line of the multiplexer tests the voltage on an electrical line between the multiplexer and the connector to determine whether or not the video signal is analog or digital.

16. A computer system comprising:

a processor operable to couple to a controller through a bus;

a video monitor coupled to the processor through the controller via the bus;

the controller operable to generate at least two video signals, the at least two video signal including an analog video signal and digital video signal;

a circuit coupled to the controller and coupled to the video monitor, the circuit operable to receive the at least two video signals from the controller; and

the circuit receives monitor identification information from the video monitor via the bus to selectively couple one of the at least two video signals.

17. The computer system of claim 16 wherein the controller is a video controller.

19. The computer system of claim 17 wherein the video controller is selected from the group consisting of a text display adapter, a graphics adapter, a 3-D graphics adapter, a SVGA display adapter, an XGA adapter, a display adapter supporting VESA graphics standards, a CGA adapter, and an adapter supporting Hercules graphics standards.

20. The computer system of claim 17 wherein the video monitor is one of a digital video monitor and an analog video monitor.

21. The computer system of claim 17 wherein a multiplexer receives both a digital and an analog video signal and sends one of a digital and analog video signal to the connector coupled between the multiplexer and the video monitor.

18. A computer system comprising:

a processor operable to couple to a video controller through a bus;

a video monitor coupled to the processor through the video controller via the bus;

the video controller operable to generate at least two video signals, the at least two video signal including an analog video signal and digital video signal;

a circuit coupled to the video controller and coupled to the video monitor, the circuit operable to receive the at least two video signals from the video controller, wherein the circuit selectively couples one of the at least two video signals to the connector based on information received from the video monitor via the bus;

the circuit includes a multiplexer coupled between the video controller and the connector, the multiplexer comprising;

select lines for selecting one of digital signal data lines, analog signal data lines, and null lines; and

a plurality of low resistance, high bandwidth analog switches;

a digital to differential circuit coupled between the video controller and the multiplexer; and

a digital to analog converter coupled between the video controller and the multiplexer.

22. A method for multiplexing an analog signal and a digital signal, the method comprising:

receiving an analog signal from a video controller at a multiplexer;

receiving a digital signal from the video controller at the multiplexer;

receiving monitor identification information from a video monitor at the multiplexer;

in response to receiving the monitor identification information, automatically determining whether the video monitor uses the digital signal or the analog signal; and

in response to determining, automatically connecting either the digital signal or the analog signal to the video monitor.

23. The method of claim 22 wherein the digital signal is one of a Low Voltage Differential Signaling (LVDS) interface and a Transition Minimized Differential Signaling (TMDS) interface.