Methods and apparatus for indicating whether a device is connected to a serial ATA communications cable

A Serial ATA communications system, comprising:

• a device;
• a Serial ATA communications cable configured to connect to the device, the Serial ATA communications cable having (i) a pair of transmit lines configured to carry a differential mode transmit signal, (ii) a pair of receive lines configured to carry a differential mode receive signal, and (iii) a set of ground lines;
• and
• a host which includes:
• a transmit circuit configured to connect to the pair of transmit lines of the Serial ATA communications cable,
• a receive circuit configured to connect to the pair of receive lines of the Serial ATA communications cable, and
• means for providing an output signal indicating whether a Serial ATA device is connected to the Serial ATA communications cable in response to a test signal applied to the set of ground lines when the transmit circuit connects to the pair of transmit lines and the receive circuit connects to the pair of receive lines;
• wherein the means for providing of the host includes:
• a cable terminal configured to connect to the set of ground lines of the Serial ATA communications cable,
• an output terminal, and
• a control circuit interconnected between the cable terminal and the output terminal, the control circuit being configured to output, as the output signal on the output terminal, (i) a first voltage level when the cable terminal connects to the device through the Serial ATA communications cable, and (ii) a second voltage level that is different than the first voltage level when the cable terminal does not connect to the device through the Serial ATA communications cable.

A host for exchanging Serial ATA communications with a device through a Serial ATA communications cable having (i) a pair of transmit lines configured to carry a differential mode transmit signal, (ii) a pair of receive lines configured to carry a differential mode receive signal, and (iii) a set of ground lines, the host comprising:

• a transmit circuit configured to connect to the pair of transmit lines of the Serial ATA communications cable;
• a receive circuit configured to connect to the pair of receive lines of the Serial ATA communications cable;
• and
• a sensor configured to provide an output signal indicating whether a device is connected to the Serial ATA communications cable in response to a test signal applied to the set of ground lines when the transmit circuit connects to the pair of transmit lines and the receive circuit connects to the pair of receive lines;
• wherein the sensor includes:
• a cable terminal configured to connect to the set of ground lines of the Serial ATA communications cable;
• an output terminal;
• and
• a control circuit interconnected between the cable terminal and the output terminal, the control circuit being configured to output, as the output signal on the output terminal, (i) a first voltage level when the cable terminal connects to the device through the Serial ATA communications cable, and (ii) a second voltage level that is different than the first voltage level when the cable terminal does not connect to the device through the Serial ATA communications cable.

A host for exchanging Serial ATA communications with a device through a Serial ATA communications cable having (i) a pair of transmit lines configured to carry a differential mode transmit signal, (ii) a pair of receive lines configured to carry a differential mode receive signal, and (iii) a set of ground lines, the host comprising:

• a transmit circuit configured to connect to the pair of transmit lines of the Serial ATA communications cable;
• a receive circuit configured to connect to the pair of receive lines of the Serial ATA communications cable;
• and
• means for providing an output signal indicating whether a device is connected to the Serial ATA communications cable in response to a test signal applied to the set of ground lines when the transmit circuit connects to the pair of transmit lines and the receive circuit connects to the pair of receive lines;
• wherein the means for providing includes:
• a cable terminal configured to connect to the set of ground lines of the Serial ATA communications cable,
• an output terminal, and
• a control circuit interconnected between the cable terminal and the output terminal, the control circuit being configured to output, as the output signal on the output terminal, (i) a first voltage level when the cable terminal connects to the device through the Serial ATA communications cable, and (ii) a second voltage level that is different than the first voltage level when the cable terminal does not connect to the device through the Serial ATA communications cable.

A method for indicating whether a device is connected to a Serial ATA communications cable having (i) a pair of transmit lines configured to carry a differential mode transmit signal, (ii) a pair of receive lines configured to carry a differential mode receive signal, and (iii) a set of ground lines, the method comprising:

• connecting a transmit circuit to the pair of transmit lines of the Serial ATA communications cable;
• connecting a receive circuit to the pair of receive lines of the Serial ATA communications cable;
• and
• when the transmit circuit connects to the pair of transmit lines and the receive circuit connects to the pair of receive lines, providing an output signal indicating whether a device is connected to the Serial ATA communications cable in response to a test signal applied to the set of ground lines;
• wherein a sensor includes a cable terminal configured to connect to the set of ground lines of the Serial ATA communications cable, an output terminal, and a control circuit interconnected between the cable terminal and the output terminal;
• and
• wherein providing the output signal includes outputting, as the output signal on the output terminal, (i) a first voltage level when the cable terminal connects to the device through the Serial ATA communications cable, and (ii) a second voltage level that is different than the first voltage level when the cable terminal does not connect to the device through the Serial ATA communications cable.