The different parts of the adapters are illustrated in Figure "Adapter Component Block Diagram", and are described below:
An Intel 80188 microprocessor controls the operation of the adapter. It translates commands received from the system into a series of operations to implement the desired results. The processor also manages the intelligent buffer, controls data transfers to and from the system, controls the SCSI bus, and handles error detection/recovery.
The program code that controls the processor is stored in a local read-only memory (ROM) module. There is also a Random Access Memory (RAM) module available for storage of work information.
The system interface controls provide command and interrupt registers that allow the processor to receive commands from the system and to interrupt the system when a command is complete.
The SCSI bus control chip is an electronic circuit module used by the processor to control the SCSI bus. It is used to transmit commands, receive status information and transfer data between the adapter card and attached SCSI devices. It also provides the following functions:
This buffer is a 512KB parity-checked RAM module, and is only available on the 32-bit high-performance version of the SCSI adapter. This buffer has two basic functions:
This circuit module manages the flow of parallel data between the SCSI bus, the intelligent buffer, and the Micro Channel. The circuit is controlled by the processor and can perform all transfers simultaneously. It supports 32-bit to 16-bit conversion, burst mode DMA, odd byte/word transfers and parity generation/checking of the buffer data.
The SCSI BIOS consists of a set of ROM modules, which contain the basic input/output support code for the adapter. It provides both the compatibility (CBIOS) and advanced (ABIOS) support for any attached SCSI fixed disk. The BIOS ROM is completely independent from the processor's ROM on the adapter. BIOS is discussed further in SCSI BIOS.