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LAN91C95

ISA/PCMCIA Full Duplex Single-Chip Ethernet and Modem Controller with RAM

SMSC -> Microchip 

GENERAL DESCRIPTION

The LAN91C95 is a VLSI Ethernet Controller

that combines ISA and PCMCIA interfaces, as

well as an interface to a companion modem chip

set, in one chip. The LAN91C95 integrates all

the MAC and physical layer functions as well as

the packet RAM needed to implement a high

performance 10BASE-T (twisted pair) node. For

10BASE5 (thick coax), 10BASE2 (thin coax),

and 10BASE-F (fiber) implementations, the

LAN91C95 interfaces to external transceivers

via its AUI port. Only one additional IC is

required on most applications.

The LAN91C95 occupies 16 I/O locations and

no memory space except for PCMCIA attribute

memory space. The same I/O space is used for

both ISA and PCMCIA operations. The

LAN91C95 can directly interface the ISA and

PCMCIA buses and deliver no wait state

operation. Its shared memory is sequentially

accessed with 40ns access times to any of its

registers, including its packet memory. No DMA

services are used by the LAN91C95; virtually

decoupling network traffic from local or system

bus utilization.

For packet memory

management, the LAN91C95 integrates a

unique hardware Memory Management Unit

(MMU) with enhanced performance and

decreased software overhead when compared to

ring buffer and linked list architectures. The

LAN91C95 is portable to different CPU and bus

platforms due to its flexible bus interface, flat

memory structure (no pointers), and its loosely

coupled buffered architecture (not sensitive to

latency).

The LAN91C95 interfaces directly with Rockwell

International L39/C39 controller-based modems

and Lucent Technologies’ HSM288xCF modem.

OVERVIEW

A unique architecture allows the LAN91C95 to

combine high performance, flexibility, high

integration and simple software interface.

I/O decoders are included in the LAN91C95’s

PCMCIA interface, with independent decoders

for the LAN and for the modem functions.

The LAN91C95 incorporates the LAN91C92/4

functionality for ISA environments with several

new features, as well as a PCMCIA interface

and attribute registers that comply with the

PCMCIA Multi-Function specification. Mode

selection between ISA and PCMCIA is static and

is done only once at the end of power on reset.

The LAN91C95 consists of the same logical I/O

register structure in ISA and PCMCIA modes.

However, some of the signals used to access

the PCMCIA differ from the ISA mode.

Additional registers exist in the PCMCIA

attribute space. The ROM memory space only

exists in ISA mode and the attribute space only

exists in PCMCIA mode.

These decoders are used whenever the

LAN91C95 is used as a multi-function card, and

they can be bypassed when only one function is

enabled. The LAN91C95 also merges the LAN’s

internal interrupt source with the external

modem interrupt connected to the LAN91C95.

The MMU (Memory Management Unit)

architecture used by the LAN91C95 combines

the simplicity and low overhead of fixed areas

with the flexibility of linked lists providing

improved performance over other methods.

The LAN91C95 is designed to support full

duplex switched Ethernet where transmit and

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