
Introduction
What is Covered in This Manual
SYM53C825A/53C825AE Data Manual
1-1
Chapter 1
Introduction
What is Covered in T his
Manual
T his manual combines information on the
SYM53C825A and SYM53C825AE , which are
PCI-SCSI I/O Processors. T he SYM53C825AE is
a minor modification of the existing
SYM53C825A product. It has all the functionality
of the SYM53C825A with the addition of features
to enable it to comply with Microsoft’s PC 97
Hardware Design Guide. Specifically, the
SYM53C825AE has a Power Management Sup-
port enhancement. Because there are only slight
differences between them, the SYM53C825A and
SYM53C825AE are referred to as SYM53C825A
throughout this data manual. Only the new
enhancements are referred to as SYM53C825AE.
It is intended for system designers and program-
mers who are using this device to design a SCSI
port for PCI-based personal computers, worksta-
tions, or embedded applications.
T his chapter includes general information about
the SYM53C825A and other members of the
SYM53C8X X family of PCI-SCSI I/O Processors.
Chapter 2 describes the main functional areas of
the chip in more detail, including the interfaces to
the SCSI bus. Chapter 3 describes the chip’s con-
nection to the PCI bus, including the PCI com-
mands and configuration registers supported.
Chapter 4 contains the pin diagrams and defini-
tions of each signal. Chapter 5 describes each bit
in the operating registers, organized by address.
Chapter 6 defines all of the SCSI SCRIPT S
instructions that are supported by the
SYM53C825A. Chapter 7 contains the electrical
characteristics and AC timings for the chip. T he
appendixes contain a register summary, a mechan-
ical drawing of the SYM53C825A, and several
example interface drawings to connect the
SYM53C825A to an external ROM.
T his data manual assumes the user is familiar with
the current and proposed standards for SCSI and
PCI. For additional background information on
these topics, please refer to the list of reference
materials provided in the Preface of this docu-
ment.
General Description
T he SYM53C825A PCI-SCSI I/O Processor
brings high-performance I/O solutions to host
adapter, workstation, and general computer
designs, making it easy to add SCSI to any PCI
system. It provides a local memory bus for local
storage of the device’s BIOS ROM in flash mem-
ory or standard EPROMs. T he SYM53C825A
also supports Big and Little Endian byte address-
ing to accommodate a variety of data configura-
tions. T he SYM53C825A supports programming
of local FLASH memory for updates to BIOS or
SCRIPT S programs.
T he SYM53C825A is a pin-for-pin replacement
for the SYM53C825 PCI-SCSI I/O processor,
although some software enhancements are needed
to take advantage of the features in the
SYM53C825A. T he SYM53C825A performs
fast 8- or 16- bit SCSI transfers in single-ended or
differential mode, and improves performance by
optimizing PCI bus utilization. A system diagram
showing the connections of the SYM53C825A
with an external ROM or flash memory is pictured
in Figure 1-1. A block diagram of the
SYM53C825A is pictured in Figure 1-2 on page
1-6.