Methods and apparatus for driving a display device

1. A transmitter for transmitting control characters to a display device via an interface comprising:

a transmitter portion configured to transmit at least one control character having a plurality of bit values and at least one separate rebalancing control character to the display device, the at least one control character representing inactive video information; and

logic configured to determine values of the bits in the control character and construct the at least one rebalancing control character based on the determination of the values of the bits in the control character, the at least one rebalancing control character constructed to have bit values selected such that the combination of the control character and the rebalancing control character are DC balanced.

2. The transmitter as defined in claim 1 , wherein the interface is an AC-coupled interface.

3. The transmitter as defined in claim 1 , wherein the interface is an interface operating according to the PCI Express standard.

4. The transmitter as defined in claim 1 , wherein the logic is further configured to select the bits of rebalancing control characters such that the total number of zero value and one value bits are equal in the aggregate of the control character and the rebalancing control character to achieve the DC balancing over the interface.

5. The transmitter as defined in claim 1 , wherein the at least one control character is at least a portion of vertical and horizontal synchronization information and the at least rebalancing control character are transmitted during a time interval when active display data is not transmitted to the display device.

6. The transmitter as defined in claim 1 , wherein the transmitter is configured to include at least the transmitter portion in a coupling device configured to couple with a PCI Express coupling.

7. The transmitter of claim 1 wherein the transmitter transmits several control characters and one rebalancing control character associated with the several control characters.

8. The transmitter of claim 1 wherein the rebalancing control character precedes or follows a control character.

9. Bridge circuitry comprising:

integrated graphics circuitry; and

an interface configured to receive a coupling having a transmitter portion for transmitting control characters to a display device via the interface, where the transmitter portion is configured to transmit at least one control character having a plurality of bit values and at least one separate rebalancing control character to the display device, the at least one control character representing inactive video information; and

logic configured to determine values of the bits in the control character and construct the at least one rebalancing control character based on the determination of the values of the bits in the control character, the at least one rebalancing control character constructed to have bit values selected such that the combination of the control character and the rebalancing control character are DC balanced.

10. The bridge circuitry as defined in claim 9 , wherein the interface is an AC-coupled interface.

11. The bridge circuitry as defined in claim 9 , wherein the interface is an interface operating according to the PCI Express standard.

12. The bridge circuitry as defined in claim 9 , wherein the logic is configured to select the bits of the rebalancing control characters such that the total number of zero value and one value bits are equal in the aggregate of the control character and the rebalancing control character to achieve the DC balancing over the interface.

13. The bridge circuitry as defined in claim 9 , wherein the at least one control character is at least a portion of vertical and horizontal synchronization information and the at least rebalancing control character are transmitted during a time interval when active display data is not transmitted to the display device.

14. The bridge circuitry as defined in claim 9 , wherein the bridge circuitry is a northbridge and wherein the interface includes a PCI Express coupling and the coupling device is configured to include at least a transmitter portion in a coupling device configured to couple with the PCI Express coupling.

15. A method for transmitting control characters for driving a display device over an interface comprising:

transmitting at least one control character to a display device;

determining the values of the bits in the at least one control character; and

transmitting at least one separate rebalancing control character with the at least one control character, the rebalancing control character constructed based on the determination of the values of the bits in the at least one control character such that the combination of the at least one control character and the at least one rebalancing control character have DC balance, the at least one control character representing inactive video information.

16. The method as defined in claim 15 , wherein the interface is an AC-coupled interface.

17. The method as defined in claim 15 , wherein the interface is an interface operating according to the PCI Express standard.

18. The method as defined in claim 15 , comprising selecting the bits of rebalancing control characters such that the total number of zero value and one value bits are equal in the aggregate of the control character and the rebalancing control character to achieve the DC balancing over the interface.

19. The method as defined in claim 15 , wherein the at least one control character is at least a portion of vertical and horizontal synchronization information and the at least rebalancing control character are transmitted during a time interval when active display data is not transmitted to the display device.

20. The method as defined in claim 15 , wherein the transmitter is configured to include at least the transmitter portion in a coupling device configured to couple with a PCI Express coupling.