METHOD AND SYSTEM FOR RESPONDING TO SIGNAL IN SYSTEM

摘要

PROBLEM TO BE SOLVED: To select a fast-exit mode for continuing operation of a DLL circuit or a slow-exit mode for suspending the operation of the DLL circuit, on-the-fly, at power-down.SOLUTION: A system comprises: a power-down control circuit 100 for suspending operation of a predetermined internal circuit in response to a power-down command; and an external terminal 14 to which a selection signal A12 is input from outside simultaneously with issuance of the power-down command. The power-down control circuit 100 suspends operation of a DLL circuit 23 when the selection signal A12 is at a low level, and continues the operation of the DLL circuit 23 when the selection signal A12 is at a high level. By using the selection signal A12 input simultaneously with the power-down command, mode selection can be made on-the-fly.