Semiconductor device performing loopback operation

An apparatus comprising:

• a first circuit configured to intermittently receive a plurality of write data sets each including a plurality of write data received in serial from outside responsive to a plurality of write commands, respectively;
• a second circuit configured to select one or ones of the plurality of write data from each of the plurality of write data sets based on a selection signal and loopback the selected one or ones of the plurality of write data to outside;
• and
• a third circuit configured to generate the selection signal,
• wherein the third circuit is configured to prevent a value of the selection signal from changing while the first circuit receives any of the plurality of write data sets.

An apparatus comprising:

• a first circuit configured to receive a first plurality of write data in a first period and receive a second plurality of write data in a second period after the first period;
• a second circuit configured to activate an enable signal in a third period between the first period and the second period;
• and
• a third circuit configured to change a state of a selection signal indicating a phase of the second plurality of write data under a condition that the enable signal is in an active state,
• wherein the second circuit is configured to prevent the enable signal from activating in the first period.