A hard disk controller integrated circuit of a SCSI target device comprises a sequencer which causes a SCSI bus to transition from a command bus phase to a data transfer bus phase during execution of an autoread or an autowrite SCSI command without waiting for a communication from a microprocessor of the SCSI target device. In some embodiments, the command is determined to be either an autotransfer command or a non-autotransfer command. If the command is a non-autotransfer command, then the sequencer does not proceed directly to the data transfer phase but rather requires microprocessor intervention before proceeding to the data transfer phase. In some embodiments, an autotransfer command (such as an autoread or an autowrite command) is carried out by the disk drive controller integrated circuit with only two interrupts being generated to the microprocessor: one after receiving the autotransfer command from the initiator; and one after data transfer of the autotransfer command is complete. The hard disk controller integrated circuit automatically sends the status byte and command complete message if there is no queue tag collision as indicated by a cleared tag not okay flag.