The MB86606A is an intelligent SCSI protocol controller (SPC) conforming to the ANSI (FAST-20) standard and integrating a PCI local bus interface function. The specification of SCSI controller block is based on the MB86605's one which is a Wide SCSI protocol controller, but the device functions/features to achieve the FAST-20 data transfer rate of maximum 40 Mbyte/sec at 16-bit FAST-20 SCSI, such as the size of internal data register FIFO, are larged on the MB86606A. As for the SCSI bus pins, a totem pole type single-ended driver/ receiver is incorporated in the device so that it can drive the SCSI bus directly. Furthermore, the MB86606A is capable of connecting the external differential type driver/receiver. The SCSI bus sequence is controlled by commands issued via the system interface. So, it supports sequential commands that perform the phase-to-phase sequences to reduce the overhead of system's sequence operations.