A serial input processing apparatus provides how to capture serial data without loss of a single bit while command interpretation is being performed in a command decoder at high frequency. Individual bytes of serial bits of a pre-defined sequence are latched and bit streams are temporarily stored with multiple clocks. The temporary store is conducted before transferring byte information to assigned address registers to register the address. The address registration and the data registration are performed by latching all bit streams of the serial input at the leading edges of clocks. While at a high frequency operation (e.g., 1 GHz or 1 ns cycle time), no additional registers are required for storing bit data during command interpretation with enough time margins between the command bit stream interpretation and next bit data stream.