Abstract: A device interface circuit unit transfers a command and data in packet format between the unit and the host. A transport layer is provided with a receive FIFO, a command detection circuit and a send FIFO, and an application layer is provided with a receive task file register and a send task control file register. An available time is generated for each break point of a packet during data transfer in order to receive another command packet from the host. When the command packet is received from the host in the available time during data transfer, the data transfer is suspended and the received command is decoded to execute a process for continuing or canceling the data transfer, after which the data transfer is resumed.

Abstract: Information about an attribute of packets that are receivable corresponding to a command is registered. When a packet is received, information about an attribute of the packet received is acquired. Upon occurrence of a reception error that there is no information in the attribute registering unit corresponding to the information acquired by the attribute acquiring unit, a predetermined reception error handling routine is executed according to a type of the reception error.

Abstract: A power saving of a serial interface circuit decreases the unnecessary power consumption of a serial interface circuit, while decreasing the return time and expanding the power saving range. Gates are disposed for stopping the clock supply to a digital portion of the interface circuit while maintaining operation of clock sources in the digital portions. Therefore a quick shift to and return from the power save mode by stopping and restarting clocks is implemented, which further decreases power consumption.

Abstract: A power saving of a serial interface circuit decreases the unnecessary power consumption of a serial interface circuit, while decreasing the return time and expanding the power saving range. Gates are disposed for stopping the clock supply to a digital portion of the interface circuit while maintaining operation of clock sources in the digital portions. Therefore a quick shift to and return from the power save mode by stopping and restarting clocks is implemented, which further decreases power consumption.

Abstract: A device interface circuit unit transfers a command and data in packet format between the unit and the host. A transport layer is provided with a receive FIFO, a command detection circuit and a send FIFO, and an application layer is provided with a receive task file register and a send task control file register. An available time is generated for each break point of a packet during data transfer in order to receive another command packet from the host. When the command packet is received from the host in the available time during data transfer, the data transfer is suspended and the received command is decoded to execute a process for continuing or canceling the data transfer, after which the data transfer is resumed.

Abstract: Information about an attribute of packets that are receivable corresponding to a command is registered. When a packet is received, information about an attribute of the packet received is acquired. Upon occurrence of a reception error that there is no information in the attribute registering unit corresponding to the information acquired by the attribute acquiring unit, a predetermined reception error handling routine is executed according to a type of the reception error.

Abstract: A storage apparatus comprises a CPU that provides read/write control of data from/into a magnetic disk, a PLL circuit that generates clock signals having different frequencies, and a selector which selects a clock signal from among the clock signals generated by the PLL circuit according to a control status of the CPU.