Emulex MD21/S2, Technical Manual

Page: 13 / 88

Section 2
GENERAL DESCRIPTION
2.1 INTRODUCTION
This section provides brief overviews of the major components of
the MD21 Disk Controller subsystem. For more specific information
about the SCSI Bus Interface and about the ESDI Interface, please
refer to the ANSI SCSI Specification and the Enhanced Small Device
Interface Specification listed on page vii.
For reference convenience, Section 2 is divided into five
subsections, as listed in the following table:
Subsection Title
2.1 Introduction
2.2
Disk Controller Overview
2.3 SCSI Bus Overview
2.4
ESDI Overview
2.5 Compatibility
2.2 MD21 DISK CONTROLLER OVERVIEW
2.2.1 PHYSICAL DESCRIPTION
The MD21 Controller, shown in Figure 2-1, is assembled on a single
board approximately 14.6 centimeters by 20.3 centimeters (5.25
inches by 7.75 inches). It can be installed directly on a mounting
bracket located in the subsystem that contains an ESDI 5.25-inch
Winchester disk drive. The MD21 Controller contains the following
major components:
• Two Emulex custom Very Large Scale Integrated (VLSI) chips:
a Buffer Controller and a disk formatter.
• An 8031 microprocessor chip
• A 32-kilobyte (K byte) Erasable Programmable Read Only
Memory (EPROM), and a 32K byte Random Access Memory (RAM)
for data buffering.
Figure 2-1 shows the MD21 Disk Controller and its components.
General Description 2-1