Semiconductor memory device, method of controlling read preamble signal thereof, and data transmission system
A system, includes a controller comprising a plurality of first external terminals configured to supply a command and an address, and communicate a data, and communicate a strobe signal related to the data; and a semiconductor memory device including a plurality of second external terminals corresponding to the plurality of first external terminals, at least one of the plurality of first external terminals and at least one of the plurality of second external terminals each being capable of supplying an information specifying a length of a preamble of the strobe signal before the semiconductor memory device communicates the data between the controller and the semiconductor memory device, the semiconductor memory device further including a preamble register configured to be capable of storing the information.
1. A method for transferring data from a first semiconductor device to a second semiconductor device comprising:
setting desired preamble length information in a register, wherein the desired preamble length information is a selected one of a plurality of possible preamble lengths;
providing a preamble having a duration specified by the desired preamble length information followed by a toggle signal having a burst length on a data strobe terminal of the first semiconductor device;
providing data in synchronization with the toggle signal on a data terminal of the first semiconductor device;
receiving the preamble and the toggle signal on a data strobe terminal of the second semiconductor device;
activating a gate connected to the data strobe terminal of the second semiconductor device during the preamble to provide a gated clock; and
receiving the data on a data terminal of the second semiconductor device in synchronization with the gated clock.
2. The method as claimed in claim 1 wherein the register is a mode register.
3. The method as claimed in claim 1 wherein the register is located in the first semiconductor device.
4. The method as claimed in claim 3 wherein the second semiconductor device sets the desired preamble length information in the register.
5. The method as claimed in claim 1 wherein the first semiconductor device is a memory device and the data is read data.
6. The method as claimed in claim 1 wherein the data terminal of the first semiconductor device and the data terminal of the second semiconductor device are bidirectional data terminals.
7. The method as claimed in claim 1 wherein the data strobe terminal of the first semiconductor device and the data strobe terminal of the second semiconductor device are bidirectional data strobe terminals.
8. The method as claimed in claim 1 wherein the preamble comprises a first logic level for the duration specified by the desired preamble length information.
9. The method as claimed in claim 8 wherein the first logic level is a low logic level.
10. The method as claimed in claim 1 wherein the plurality of possible preamble lengths comprise a first possible preamble length of one period of a system clock and a second possible preamble length of two periods of the system clock.
11. The method as claimed in claim 1 further comprising setting the data strobe terminal of the first semiconductor device to a high impedance state before the preamble.
12. The method as claimed in claim 1 further comprising providing a postamble following the toggle signal on the data strobe terminal of the first semiconductor device.
13. The method as claimed in claim 12 further comprising setting the data strobe terminal of the first semiconductor device to a high impedance state before the preamble and after the postamble.