Abstract: The host adapter integrated circuit is a one chip high performance bus master host adapter for (i) connecting a first bus having a specified protocol for transferring information over the first bus and a first data transfer speed to a second bus having a specified protocol for transferring information over the second bus and a second data transfer speed, and (ii) transferring information between the two buses. The host adapter integrated circuit, hereinafter host adapter, includes a novel reduced instruction set computing (RISC) processor, a first interface module circuit connectable to the first bus and coupled to the RISC processor, a second interface module circuit connectable to the second bus and coupled to the RISC processor, and a memory circuit means connected to the first interface module circuit and to the second interface module circuit and coupled to the RISC processor.

Abstract: A single chip circuit is used in combination with a host system microprocessor to provide host-adapter functions for a SCSI interface. The host adapter integrated circuit includes a 128 byte DMA FIFO, a 8 byte SCSI FIFO, hardwired automatic sequencers for the SCSI ARBITRATION and SELECTION phases, hardware interrupt generating circuitry, two clock sources, a register set and a powerdown capability. The host computer system microprocessor is used to perform selected SCSI phases. Other SCSI phases are performed automatically by the integrated circuit of this invention. When a delay in a SCSI phase is anticipated, according to the principles of this invention control of the microprocessor is returned to the host computer system. Hence, the microprocessor may execute a user application while the integrated circuit simultaneously performs one or more SCSI phases. When the SCSI phase is complete or other predetermined conditions occur on the SCSI bus, a hardware interrupt is sent to the microprocessor.