LXT914
—
Flexible Quad Ethernet Repeater
14
Datasheet
2.0
Functional Description
2.1
Introduction
The LXT914 is an integrated hub repeater for 10BASE-T networks. The hub repeater is the central
point for information transfer across the network. The LXT914 offers multiple operating modes to
suit a broad range of applications ranging from simple 4-port stand-alone hubs or attachments for
print and file servers, up to intelligent 128-port enterprise systems with microprocessor/gate array
management.
The main functions of the LXT914 hub repeater are data recovery and re-transmission and
collision propagation. Data packets received at the AUI or 10BASE-T ports are detected and
recovered by the port receivers before being passed to the repeater core circuitry for re-timing and
re-transmission. Data packets received through the IRB port are essentially passed directly to the
core for retransmission. After recovery of a valid data packet, the repeater broadcasts it to all
enabled stations, except the originator station.
2.2
External Interfaces
The LXT914 includes four 10BASE-T ports with internal filters. The LXT914 also includes an
Attachment Unit Interface (AUI) port, a serial port and an Inter-Repeater Backplane (IRB) port.
The serial port allows an external device such as an EEPROM to download setup parameters to the
repeater. In more complex designs the serial port can also be used to monitor repeater status. The
IRB port enables multiple LXT914 devices to be cascaded, creating a large, multi-port repeater.
2.2.1
10BASE-T Ports
The four 10BASE-T transceiver ports are completely self-contained. Since the transmitters and
receivers include the required filtering, only simple, inexpensive transformers are required to
complete the 10BASE-T interface. Each individual Twisted-Pair (TP) port is implemented in
accordance with the IEEE 802.3 10BASE-T standard.
2.2.2
AUI Port
The AUI port mode is selectable (DTE mode or MAU mode). With DTE mode selected, the AUI
port allows connection of an external transceiver (10BASE2, 10BASE5, 10BASE-T or FOIRL) or
a drop cable. With MAU mode selected, the AUI port establishes a MAU output allowing direct
connection to another DTE interface.