Patent ID: 6853239

Claim:
A semiconductor integrated circuit device comprising; a first circuit block having first and second modes: a second circuit block: and an interface circuit provided between an output of the first circuit block and an input of the second circuit block; wherein the interface circuit includes a storage unit to hold a state of the output of the first circuit block and a signal gate unit which is provided between the storage unit and the output of the first circuit block, wherein a first power supply voltage is applied to the first circuit block in the first mode and the first power supply voltage is stopped to apply to the first circuit block in the second mode, wherein the signal gate unit connects the storage unit to the output of the first circuit block in the first mode and the signal gate unit disconnects the storage unit from the output of the first circuit block in the second mode, wherein the first circuit block includes a plurality of registers, and wherein values of the registers are saved when the first circuit block changes from the first mode to the second mode.