Receiver training during a SATA out of band sequence
A communications apparatus is provided having a first line driver transmitting data at a first end of a serial bus to a second line receiver at a second end of the serial bus. A first line receiver receives data at the first end of the serial bus from a second line driver at the second end of the serial bus. The first line receiver has a selectable input parameter that controls a physical layer quality of data received at the first end of the serial bus. Programming instructions stored in memory cause the second line driver to transmit a training signal that is not a COMWAKE signal to the first line receiver in response to the first line driver transmitting a COMWAKE signal to the second line receiver. A controller compares a received physical layer quality of the training signal at the first line receiver to a desired physical layer quality and computes a value for the input parameter to obtain a desired physical layer quality.
1. A method comprising:
a first device transmitting a COMWAKE signal to a second device via a serial bus;
in response to the first device transmitting the COMWAKE signal, the second device transmitting a training signal that is not a COMWAKE signal to the first device via the serial bus;
after transmitting the training signal, setting a first parameter value based on a characterization of the training signal to obtain a desired physical layer quality between the first and second devices; and
after setting the first parameter value, transmitting a second training signal that is not a COMWAKE signal to the second device via the serial bus before the second device transmits a COMWAKE signal to the first device.
2. The method of claim 1 wherein the first parameter is a control input to a transceiver connecting the first device to a first end of the serial bus.
3. The method of claim 1 wherein the first parameter value is a dB value associated with a pre-emphasis physical layer quality.
4. The method of claim 1 wherein the first parameter value is a gain value associated with an amplitude physical layer quality.
5. The method of claim 1 further comprising after transmitting the second training signal, setting a second parameter value based on a characteristic of the second training signal to obtain the desired physical layer quality between the first and second devices before the second device transmits a COMWAKE signal to the first device.
6. The method of claim 5 further comprising the second device, if it does not receive the second training signal, transmitting a third training signal to the first device via the serial bus before the second device transmits a COMWAKE signal to the first device.
7. The method of claim 6 further characterized by the third training signal having a different bit transmission rate than the first training signal.
8. The method of claim 5 further comprising after setting the second parameter value, the second device aborting the first training signal and then transmitting a COMWAKE signal to the first device via the serial bus.
9. The method of claim 5 wherein the second parameter is a control input to a transceiver connecting the second device to a second end of the serial bus.
10. The method of claim 5 wherein the second parameter value is a dB value associated with a pre-emphasis physical layer quality.
11. The method of claim 5 wherein the second parameter value is a gain value associated with an amplitude physical layer quality.
12. A method comprising:
a first device transmitting a COMWAKE signal via a serial bus;
in response to the transmitting the COMWAKE signal, the first device receiving a first training signal via the serial bus; and
setting a first receiver parameter to a value based on a characteristic of the first training signal to obtain a desired physical layer quality before the first device receives a COMWAKE signal via the serial bus.
13. The method of claim 12 wherein the first receiver parameter value is a dB value associated with a pre-emphasis physical layer quality.
14. The method of claim 12 wherein the first receiver parameter value is a gain value associated with an amplitude physical layer quality.
15. The method of claim 12 further comprising after setting the first receiver parameter value, transmitting a second training signal via the serial bus before the first device receives a COMWAKE signal via the serial bus.
16. The method of claim 15 further comprising after transmitting the second training signal, setting a second receiver parameter value based on information in the second training signal to obtain the desired physical layer quality before the first device transmits a COMWAKE signal via the serial bus.
17. The method of claim 16 further comprising in response to the transmitting the second training signal, receiving a third training signal via the serial bus before receiving a COMWAKE signal via the serial bus.
18. The method of claim 17 further characterized by the third training signal having a different bit transmission rate than the first training signal.
19. The method of claim 16 further comprising after setting the second receiver parameter value, aborting the first training signal and then receiving a COMWAKE signal via the serial bus.
20. A communications apparatus comprising:
a first line driver transmitting data at a first end of a serial bus to a second line receiver at a second end of the serial bus;
a first line receiver receiving data at the first end of the serial bus from a second line driver at the second end of the serial bus, the first line receiver having a selectable input parameter that controls a physical layer quality of data received at the first end of the serial bus;
programming instructions stored in memory that causes the second line driver to transmit a training signal that is not a COMWAKE signal to the first line receiver in response to the first line driver transmitting a COMWAKE signal to the second line receiver; and
a controller that compares a received physical layer quality of the training signal at the first line receiver to a desired physical layer quality and computes a value for the input parameter to obtain a desired physical layer quality.