AM79C974 datasheet(2/153 Pages) AMD

2 / 153 page

AMD

P R E L I M I N A R Y

Am79C974

The PCnet-SCSI is part of AMD’s PCI product family of

plug-in and software compatible SCSI and Ethernet

controllers. This product compatibility ensures a low

cost system upgrade path and lower motherboard

manufacturing costs.

Ethernet Specific

The PCnet-SCSI controller includes a complete Ether-

net node integrated into a single VLSI device. It contains

a bus interface unit, a DMA buffer management unit, an

IEEE 802.3-defined Media Access Control (MAC) func-

tion, individual 136-byte transmit and 128-byte receive

FIFOs, an IEEE 802.3-defined Attachment Unit Inter-

face (AUI) and Twisted-Pair Transceiver Media Attach-

ment Unit (10BASE-T MAU), and a Microwire EEPROM

interface. The PCnet-SCSI controller is also register

compatible with the LANCE (Am7990) Ethernet control-

ler, the C-LANCE (Am79C90) Ethernet controller, the

ILACC (Am79C900) Ethernet controller, and all Ether-

net controllers in the PCnet Family, including the PCnet-

ISA controller (Am79C960), the PCnet-ISA+ controller

(Am79C961),

and

the

PCnet-32

controller

(Am79C965). The buffer management unit supports the

LANCE, ILACC, and PCnet descriptor software models.

The PCnet-SCSI controller is software compatible with

the Novell NE2100 and NE1500 Ethernet adapter card

architectures. In addition, a Sleep function has been in-

corporated to provide low standby current, excellent for

notebooks and Green PCs.

The 32-bit multiplexed bus interface unit provides a di-

rect interface to the PCI local bus applications, simplify-

ing the design of an Ethernet node in a PC system. With

its built-in support for both little and big endian byte

alignment, this controller also addresses proprietary

non-PC applications.

The PCnet-SCSI controller supports auto configuration

in the PCI configuration space. Additional PCnet-SCSI

controller configuration parameters, including the

unique IEEE physical address, can be read from an ex-

ternal non-volatile memory (serial EEPROM) immedi-

ately following system RESET.

The controller also has the capability to automatically

select either the AUI port or the Twisted-Pair trans-

ceiver. Only one interface is active at any one time. The

individual transmit and receive FIFOs optimize system

overhead, providing sufficient latency during frame

transmission and reception, and minimizing intervention

during normal network error recovery. The integrated

Manchester encoder/decoder (MENDEC) eliminates

the need for an external Serial Interface Adapter (SIA) in

the system. In addition, the device provides program-

mable on-chip LED drivers for transmit, receive, colli-

sion, receive polarity, link integrity or jabber status.

SCSI Specific

The PCnet-SCSI controller also includes a high-

performance Fast SCSI controller with a glueless inter-

face to the PCI local bus. The PCnet-SCSI integrates its

own 32-bit bus mastering DMA engine with an industry

standard Fast SCSI-2 block. The DMA engine and ac-

companying 96 byte DMA FIFO allow 32-bit burst data

transfers across the high bandwidth PCI bus at speeds

of up to 132 Mbyte/s. Full support for scatter-gather

DMA transfers optimize performance in multi-tasking

system applications.

The PCnet-SCSI’s on-chip state machine controls SCSI

bus sequences in hardware and is coupled with the bus

mastering DMA engine to eliminate the need for an on-

chip RISC processor. This results in a smaller die size

giving the Am79C974 superior price/performance ver-

sus competitive offerings.

AMD supports the Am79C974 with a total system solu-

tion which includes:

A full suite of licensable SCSI drivers and utilities

fully tested under the following operating system

environments:

— DOS 5.0 – 6.0

— Windows 3.1

— Windows NT

— OS/2 2.x

— Netware 3.x, 4.x

— SCO UNIX 3.2.4, ODT 2.0

An INT13h Compatible SCSI ROM BIOS

ASPI Compatibility

Complete hardware reference design kit

For more detailed information on the PCnet-SCSI refer

to the technical manual, PID #18738A.

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