Memory Devices, Systems and Methods Employing Command/Address Calibration

1. A method of interface training, comprising: sending a first calibration signal to a semiconductor device over a command/address bus, sending a clock signal to the semiconductor device with the sending of the first calibration signal, the clock signal providing a timing to the semiconductor device to latch logic levels of the first calibration signal; receiving a second calibration signal from the semiconductor device over a data bus, the second calibration signal being derived from latched logic levels of the first calibration signal, sending command and address signals over the command/address bus to the semiconductor device with the sending of the clock signal, a phase between the command and address signals and the clock signal being responsive to the second calibration signal; and sending a read request signal over a first line separate from the command/address bus to the semiconductor device while sending the first calibration signal.

2. The method of claim 1, further comprising sending a read request signal over a first line separate from the command/address bus to the semiconductor device while sending the first calibration signal.

3. The method of claim 2 claim 1, wherein the first line is a clock enable line.

4. The method of claim 1, wherein the first calibration signal comprises a sequence of data packets transmitted at a rate at least twice that of the period of the clock signal.

5. The method of claim 1, wherein the sending of a first calibration signal to the semiconductor device comprises sending a training pattern over each of multiple lines of the command/address bus.

6. The method of claim 5, wherein the training pattern is the same for each of the multiple lines of the command/address bus.

7. The method of claim 5, wherein the sending of the command and address signals over the command/address bus comprises individually adjusting the phase between the command and address signals and the clock signal for each of the multiple lines of the command/address bus.

8. The method of claim 5, wherein the sending of the command and address signals over the command/address bus comprises sending a first signal over a first line of the command/address bus with a first phase with respect to the clock signal and sending a second signal over a second line of the command/address bus with a second phase with respect to the clock signal.

9. The method of claim 1, wherein the sending the command/address signal of the command and address signals comprises sending over each of a majority of lines of the command/address bus both address information and command information.

10. The method of claim 1, wherein the semiconductor device is a first semiconductor device, and wherein the method further comprises: sending a third calibration signal to a second semiconductor device over the command/address bus, sending the clock signal to the second semiconductor device with the sending of the third calibration signal, the clock signal providing a timing to the second semiconductor device to latch logic levels of the third calibration signal; receiving a fourth calibration signal from the second semiconductor device over the data bus, the fourth calibration signal being derived from latched logic levels of the third calibration signal; and sending command and address signals over the command/address bus to the second semiconductor device with the sending of the clock signal, a phase between the command and address signals and the clock signal being responsive to the fourth calibration signal.

11. A method of interface training comprising: sending a calibration command to a semiconductor device over a command/address bus together with activation of a chip selection signal for entering into a calibration mode; after entering into the calibration mode, sending a first calibration signal to the semiconductor device over the command/address bus; sending a clock signal to the semiconductor device with the sending of the first calibration signal, the clock signal providing a timing to the semiconductor device to latch logic levels of the first calibration signal; receiving a second calibration signal from the semiconductor device over a data bus, the second calibration signal being derived from latched logic levels of the first calibration signal; and sending command and address signals over the command/address bus to the semiconductor device with the sending of the clock signal, a phase between the command and address signals and the clock signal being responsive to the second calibration signal, wherein sending the calibration command is performed by sending the same calibration command signals corresponding to the calibration command multiple times including at a rising edge of the clock signal and a falling edge of the clock signal that are consecutive to each other.

12. The method of claim 11, wherein sending the calibration command is performed by sending the same calibration command signals corresponding to the calibration command only twice at the consecutive rising edge and falling edge of the clock signal.

13. The method of claim 11, wherein the chip selection signal is activated with a logic low level.

14. The method of claim 13, wherein the chip selection signal maintains an active state during the sending of the calibration command.

15. The method of claim 13, wherein the chip selection signal is activated with the sending of the first calibration signal.

16. The method of claim 15, further comprising, during the calibration mode: sending a third calibration signal over the command/address bus; receiving a fourth calibration signal over the data bus, the fourth calibration signal being derived from latched logic levels of the third calibration signal; and deactivating the chip selection signal with a logic high level during a period between the first calibration signal and the third calibration signal.

17. The method of claim 11, wherein sending the same calibration command signals multiple times reduces possibility of failure to recognize the calibration command correctly.

18. The method of claim 11, wherein the sending of a first calibration signal to the semiconductor device comprises sending a training pattern over each of multiple lines of the command/address bus.

19. The method of claim 18, wherein the training pattern is the same for each of the multiple lines of the command/address bus.

20. The method of claim 18, wherein the sending of the command and address signals over the command/address bus comprises individually adjusting the phase between the command and address signals and the clock signal for each of the multiple lines of the command/address bus.

21. The method of claim 18, wherein the sending of the command and address signals over the command/address bus comprises sending a first signal over a first line of the command/address bus with a first phase with respect to the clock signal and sending a second signal over a second line of the command/address bus with a second phase with respect to the clock signal.

22. The method of claim 11; wherein the sending of the command and address signals comprises sending over each of a majority of lines of the command/address bus both address information and command information.

23. The method of claim 11; wherein the semiconductor device is a first semiconductor device; and wherein the method further comprises: sending a third calibration signal to a second semiconductor device over the command/address bus; sending the clock signal to the second semiconductor device with the sending of the third calibration signal, the clock signal providing a timing to the second semiconductor device to latch logic levels of the third calibration signal; receiving a fourth calibration signal from the second semiconductor device over the data bus; the fourth calibration signal being derived from latched logic levels of the third calibration signal; and sending command and address signals over the command/address bus to the second semiconductor device with the sending of the clock signal; a phase between the command and address signals and the clock signal being responsive to the fourth calibration signal.