Electronic system and refresh method

1. An electronic system, comprising:

a plurality of dynamic semiconductor memory devices; and

a controller for controlling the semiconductor memory devices,

wherein each of the dynamic semiconductor memory devices includes:

a storage device for storing designated numbers designating an order for performing a refresh operation, the designated numbers being supplied from the controller when the electronic system is initialized;

a refresh enable signal generating circuit for generating a refresh enable signal in response to a refresh controlling command supplied from the controller; and

delay means for delaying the refresh enable signal by different time intervals which are determined by the designated numbers.

2. The system of claim 1 , wherein the delay means includes:

a decoder for generating decoded signals by decoding the designated numbers;

a delaying circuit for outputing delayed signals by delaying the refresh enable signal by the different time intervals; and

a switching circuit for transmitting the refresh enable signal and one of the delayed signals in response to the decoded signals.

3. The system of claim 2 , wherein the delaying circuit includes a plurality of delay elements connected in series, each of the delay elements receiving the refresh enable signal and generating a delayed signal delayed by the different time intervals.

4. The system of claim 1 , wherein the controller supplies the designated number to the dynamic semiconductor memory devices through data input output signal lines of the dynamic semiconductor memory devices.

5. The electronic system of claim 1 , wherein the plurality of dynamic semiconductor memory devices are dynamic random access memories (DRAM).

6. An electronic system, comprising:

a plurality of dynamic semiconductor memory devices; and

a controller for controlling the semiconductor memory devices,

wherein each of the dynamic semiconductor memory devices includes:

a storage device for storing a designated number designating an order for performing a refresh operation when the system is initialized;

a decoder for generating a plurality of decoded signals by decoding the designated number;

refresh enable signal generating means for generating a refresh enable signal in response to a refresh controlling command supplied from the controller;

delaying means for delaying the refresh enable signal by a time interval which is determined by the designated number;

switching means for transmitting the delayed refresh enable signal in response to the decoded signals; and

refresh address generating means for generating a refresh address in response to an output signal output from the switching means.

7. The system of claim 6 , wherein the delaying means includes a plurality of delay elements connected in series, the delay elements receiving the refresh enable signal and generating a plurality of delayed signals by delaying the refresh enable signal.

8. The system of claim 6 , wherein the controller applies the designated number to the dynamic semiconductor memory devices through a plurality of corresponding data input output signal lines.

9. The electronic system of claim 6 , wherein the plurality of dynamic semiconductor memory devices are dynamic random access memories (DRAM).

10. A method of refreshing an electronic system including a plurality of dynamic semiconductor memory devices and a controller for controlling operation of the dynamic semiconductor memory devices, comprising:

storing a designated number designating an order for performing a refresh operation on each of the plurality of dynamic semiconductor memory devices; and

performing the refresh operation on the plurality of dynamic semiconductor memory devices in an order related to the designated number when a refresh control command is applied from the controller during the refresh operation.

11. The method of claim 10 , wherein performing the refresh operation includes:

generating a plurality of decoded signals by decoding each of the designated numbers;

generating a plurality of delayed signals by delaying the refresh control command by different time intervals;

outputting the delayed signals in response to the decoded signals, respectively.

12. An electronic system for performing the method of claim 10 .