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National SemiconductorVersion A
March 1997
DP83840A 10/100 Mb/s Ethernet Physical Layer
General Description
The DP83840A is a Physical Layer device for Ethernet
10BASE-T and 100BASE-X using category 5 Unshielded,
Type 1 Shielded and Fiber Optic cables.
This VLSI device is designed for easy implementation of
10/100 Mb/s Ethernet LANs. It interfaces to the PMD sub-
layer through National Semiconductor's DP83223 Twisted
Pair Transceiver, and to the MAC layer through a Media
Independent Interface (MII), ensuring interoperability
between products from different vendors.
The DP83840A is designed with National Semiconductor's
BiCMOS process. Its system architecture is based on the
integration of several of National Semiconductor's industry
proven core technologies:
10BASE-T ENDEC/Transceiver module to provide the 10
Mb/s IEEE 802.3 functions
Clock Recovery/Generator Modules from National
Semiconductor's leading FDDI product
FDDI Stream Cipher (Cyclone)
100BASE-X physical coding sub-layer (PCS) and control
logic that integrate the core modules into a dual speed
Ethernet physical layer controller
System Diagram
Features
• IEEE 802.3 10BASE-T compatible--ENDEC and UTP/
STP transceivers and filters built-in
• IEEE 802.3u 100BASE-X compatible--support for 2 pair
Category 5 UTP (100m), Type 1 STP and Fiber Optic
Transceivers--Connects directly to the DP83223 Twisted
Pair Transceiver
• ANSI X3T12 TP-PMD compatible
• IEEE 802.3u Auto-Negotiation for automatic speed
selection
• IEEE 802.3u compatible Media Independent Interface
(MII) with Serial Management Interface
• Integrated high performance 100 Mb/s clock recovery
circuitry requiring no external filters
• Full Duplex support for 10 and 100 Mb/s
• MII Serial 10 Mb/s output mode
• Fully configurable node and repeater modes--allows
operation in either application
• Programmable loopback modes for easy system
diagnostics
• Flexible LED support
• IEEE 1149.1 Standard Test Access Port and Boundary-
Scan compatible
• Small footprint 100-pin PQFP package
• Individualized scrambler seed for multi-PHY applications
DP83840A
10/100 Mb/s Ethernet Physical Layer
10 AND/OR 100 Mb/s
ETHERNET MAC OR
REPEATER/SWITCH
PORT
DP83840A
10/100 Mb/s
ETHERNET PHYSICAL LAYER
CLOCKS
STATUS
LEDS
DP83223
100BASE-TX
TRANSCEIVER
MAGNETICS
RJ-45
10BASE-T
OR
100BASE-TX
MII
10BASE-T
100BASE-FX
TRANSCEIVER
