User`s manual

SBCSCSI/D1 2-1
2
OVERVIEW
Introduction
The following chapter is an introduction to the workings of the SIOP Firmware
which is used to control the SCSI port on the SBCs. It is recommended that the
reader have a working knowledge of SCSI.
A Basic View of the SIOP Firmware
The Firmware consists of the Motorola Microprocessor (MPU) code and the
NCR SCSI SCRIPTS code (SCRIPTS) which work together to control the NCR
53C710 SCSI I/O Processor (SIOP).
The MPU code provides the user interface to the SCSI bus. In addition, it
translates user command requests into a format executable by the SCRIPTS,
manages SIOP operating parameters, handles SIOP interrupt conditions,
manages internal command request queues, and returns status to the user.
The MPU code initiates user command requests to the SCSI bus by invoking
the SCRIPTS.
All of the MPU code is written in "C". The interfaces to the Firmware shown
in Chapter 3 are based on the "C" syntax. In addition, "C" syntax is used
throughout this manual for data structures, examples, etc. For the
convenience of assembly language users, Tables 3-2 and 3-3 show the
assembly language interface.
The SCRIPTS, which are instructions executed by the SIOP, control the
functional flow of the SIOP (i.e., transition of SCSI data and control lines). The
SCRIPTS manage the physical thread of each SCSI command request by using
the processed information provided by the MPU code to drive the SIOP.
The SIOP handles the hardware interface to the SCSI bus. The SIOP operates
in a manner which conforms to the physical requirements of the SCSI
specification.