DP8391A Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – SNI Serial Network Interface

July 1993
DP8391A NS32491A SNI Serial Network Interface
General Description
The DP8391A Serial Network Interface (SNI) provides the
Manchester data encoding and decoding functions for
IEEE 802 3 Ethernet Cheapernet type local area networks
The SNI interfaces the DP8390 Network Interface Controller
(NIC) to the Ethernet transceiver cable When transmitting
the SNI converts non-return-to-zero (NRZ) data from the
controller and clock pulses into Manchester encoding and
sends the converted data differentially to the transceiver
The opposite process occurs on the receive path where a
digital phase-locked loop decodes 10 Mbit s signals with as
much as g18 ns of jitter
The DP8391A SNI is a functionally complete Manchester
encoder decoder including ECL like balanced driver and re-
ceivers on board crystal oscillator collision signal transla-
tor and a diagnostic loopback circuit
The SNI is part of a three chip set that implements the com-
plete IEEE compatible network node electronics as shown
below The other two chips are the DP8392 Coax Transceiv-
er Interface (CTI) and the DP8390 Network Interface Con-
troller (NIC)
Incorporated into the CTI are the transceiver collision and
jabber functions The Media Access Protocol and the buffer
management tasks are performed by the NIC There is an
isolation requirement on signal and power lines between the
CTI and the SNI This is usually accomplished by using a set
of miniature pulse transformers that come in a 16-pin plastic
DIP for signal lines Power isolation however is done by
using a DC to DC converter
Features
Y _{Compatible with Ethernet II IEEE 802 3 10Base5}
10Base2 and 10Base-T
Y _{10 Mb s Manchester encoding decoding with receive}
clock recovery
Y _{Patented digital phase locked loop (DPLL) decoder re-}
quires no precision external components
Y _{Decodes Manchester data with up to} g_{18 ns of jitter}
Y _{Loopback capability for diagnostics}
Y _{Externally selectable half or full step modes of opera-}
tion at transmit output
Y _{Squelch circuits at the receive and collision inputs re-}
ject noise
Y _{High voltage protection at transceiver interface (16V)}
Y _{TTL MOS compatible controller interface}
Y _{Connects directly to the transceiver (AUI) cable}
Table of Contents
1 0 System Diagram
2 0 Block Diagram
3 0 Functional Description
3 1 Oscillator
3 2 Encoder
3 3 Decoder
3 4 Collision Translator
3 5 Loopback
4 0 Connection Diagrams
5 0 Pin Descriptions
6 0 Absolute Maximum Ratings
7 0 Electrical Characteristics
8 0 Switching Characteristics
9 0 Timing and Load Diagrams
10 0 Physical Dimensions
1 0 System Diagram
IEEE 802 3 Compatible Ethernet Cheapernet Local Area Network Chip Set
C1995 National Semiconductor Corporation TL F 9357
TL F 9357 – 1
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