Flexible processor-driven SCSI controller with buffer memory and local processor memory coupled via separate buses

A controller coupled to a local processor and a local processor memory via a first bus for providing an interface between a disk drive controller and a SCSI bus, the disk drive controller having a disk interface, said controller comprising:

• a SCSI-protocol processor having an instruction set which provides programmable control for the operation of said SCSI bus, wherein instructions are provided to said SCSI-protocol processor from an external buffer memory, said buffer memory coupled to said SCSI-protocol processor via a second bus for (i) providing temporary storage for data to be written to said disk drive, (ii) for data read from said disk drive, and (iii) for storing program data and instructions for use by said SCSI-protocol processor, wherein said SCSI-protocol processor executes one instruction in said instruction set and requests a next instruction from the external buffer memory independently from said local processor and said local processor memory;
• a buffer manager circuit coupled to said external buffer memory, to said SCSI-protocol processor, and to said disk interface, for controlling the flow of data to and from said buffer memory and allocating space within said buffer memory for the storage of program data and instructions for use by said SCSI-protocol processor and disk interface, wherein control of said external buffer memory by said buffer manager circuit is independent of the local processor and the local processor memory.