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 using a controller to access a memory device in a semiconductor memory system, the method comprising:
providing a system clock from the controller;
receiving the system clock on a system clock input terminal of the memory device;
providing desired preamble length information from the controller, wherein the desired preamble length information is a selected one of a plurality of possible preamble lengths;
receiving the desired preamble length information on address input terminals of the memory device;
issuing a read command using the controller;
receiving the read command on command input terminals of the memory device;
accessing read data from a first memory bank of the memory device;
providing a preamble having a duration specified by the desired preamble length information on a bidirectional data strobe terminal of the memory device;
providing the read data from bidirectional data terminals of the memory device in synchronization with a read toggle signal provided on the bidirectional data strobe terminal;
receiving, at the controller, the preamble having the duration specified by the desired preamble length information; and
receiving, at the controller, read data from the bidirectional data terminals of the memory device in synchronization with receiving, at the controller, the read toggle signal from the bidirectional data strobe terminal of the memory device.
2. The method as claimed in claim 1 , wherein the read toggle signal is synchronized with the system clock.
3. 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.
4. The method as claimed in claim 3 , wherein the first logic level is a low logic level.
5. The method as claimed in claim 1 , wherein the plurality of possible preamble lengths comprise a first possible preamble length of one period of the system clock and a second possible preamble length of two periods of the system clock.
6. The method as claimed in claim 1 , wherein the desired preamble length information is stored in a mode register.
7. The method as claimed in claim 6 , wherein the memory device comprises the mode register.
8. The method as claimed in claim 1 , further comprising providing an inverted system clock from the controller and receiving the inverted system clock on an inverted system clock input terminal of the memory device.
9. The method as claimed in claim 1 , further comprising:
receiving, at the controller, an inverted preamble having a duration specified by the desired preamble length information from an inverted bidirectional data strobe terminal of the memory device; and
receiving an inverted read toggle signal from the inverted bidirectional data strobe terminal of the memory device.
10. The method as claimed in claim 1 , wherein the memory device is at least one of a synchronous DRAM or a double data rate synchronous DRAM.