System and method for a switched data bus termination

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a two-wire twisted pair data cable with first and second wires having first and second ends with twisted pair bus drivers at the first and second data cable ends, the twisted pair bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the twisted pair bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first twisted pair bus receiver having first and second receiver inputs coupled to the first and second wires, respectively, at the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second twisted pair bus receiver having first and second receiver inputs coupled to the first and second wires, respectively, at the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first twisted pair termination coupled to the first and second wires, respectively, at the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second twisted pair termination coupled to the first and second wires, respectively, at the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end, whereby said first termination is inactive and said second termination is active when the data bus is in the transmitting mode and said first termination is active and said second termination is inactive when the data bus is in the receiving mode.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a data cable having first and second ends with bus drivers at the first and second data cable ends wherein the data cable includes a two-wire twisted pair having first and second wires, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination, including a resistive element, coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second termination, including a resistive element, coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end, said resistive elements each including a resistor coupled between said first and second wires of said two-wire twisted pair.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a data cable having first and second ends with bus drivers at the first and second data cable ends wherein the data cable includes a two-wire twisted pair having first and second wires, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination, including a resistive element, coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second termination, including a resistive element, coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end wherein said resistive elements each include a semiconductor switch element having a first impedance when selectively activated and a second impedance higher than said first impedance when not selectively activated and said semiconductor switch elements are coupled between said first and second wires of said two-wire twisted pair data cable.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a two-wire data cable having first and second ends with bus drivers at the first and second data cable ends, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end, said first termination coupling first and second wires of the two-wire data cable to a common reference level at the data cable first end;
• and
• a second termination coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end, said second termination coupling the first and second wires of the two-wire data cable to a common reference level at the data cable second end.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a data cable having first and second ends with bus drivers at the first and second data cable ends wherein the data cable includes a two-wire twisted pair having first and second wires, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second termination coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end wherein said first and second terminations each comprises a first termination element coupled between said first wire of said two-wire twisted pair data cable and a first reference signal and a second termination element coupled between said second wire of said two-wire twisted pair data cable and a second reference signal.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a data cable having first and second ends with bus drivers at the first and second data cable ends wherein the data cable includes a two-wire twisted pair having first and second wires, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second termination coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end wherein said first and second terminations each includes a switch coupled between said first wire of said two-wire twisted pair data cable and a termination reference, said switches being activated by switch control commands to selectively activate either said first termination or said second termination.

A system for the termination of a bidirectional serial data bus coupled between a first device and a second device, including a data cable having first and second ends with bus drivers at the first and second data cable ends, the bus driver at the data cable first end transmitting a first data signal from the data cable first end to the data cable second end when the data bus is in a transmitting mode and the bus driver at the data cable second end transmitting a second data signal from the data cable second end to the data cable first end when the data bus is in a receiving mode, the system comprising:

• a first bus receiver having a receiver input coupled to the data cable first end to receive the second data signal from the data cable second end when the data bus is in the receiving mode;
• a second bus receiver having a receiver input coupled to the data cable second end to receive the first data signal from the data cable first end when the data bus is in the transmitting mode;
• a first termination coupled to the data cable first end and selectively activated when the data bus is in the receiving mode to terminate the data cable first end;
• and
• a second termination coupled to the data cable second end and selectively activated when the data bus is in the transmitting mode to terminate the data cable second end wherein said first and second terminations each include a capacitive element operating to provide an alternating current (AC) pathway for said first and second terminations, respectively whereby said first termination is inactive and said second termination is active when the data bus is in the transmitting mode and said first termination is active and said second termination is inactive when the data bus is in the receiving mode.

A system for the termination of a computer bidirectional serial data bus, including a two-wire twisted pair data cable, having first and second ends and coupled to a first device at the first end and to a second device at the second end, the data bus having a transmitting mode to transmit data from the data bus first end to the data bus second end and a receiving mode to receive data transmitted from the data bus second end to the data bus first end, the system comprising:

• a first twisted pair termination coupled to the data bus first end and selectively activated when the data bus is in the receiving mode to terminate the data bus first end;
• a second twisted pair termination coupled to the data bus second end and selectively activated when the data bus is in the transmitting mode to terminate the data bus second end;
• and
• a bus controller to generate at least a first bus enable signal to control said first and second twisted pair terminations wherein said first twisted pair termination is inactive and said second twisted pair termination is active when the data bus is in the transmitting mode and said first twisted pair termination is active and said second twisted pair termination is inactive when the data bus is in the receiving mode.