AM7992B Datasheet, PDF (1/27 Pages) Advanced Micro Devices – Serial Interface Adapter (SIA)

FINAL
Am7992B
Serial Interface Adapter (SIA)
DISTINCTIVE CHARACTERISTICS
s Compatible with lEEE 802.3/Ethernet/Cheapernet
specifications
s Crystal/TTL oscillator-controlled Manchester
encoder
s Manchester decoder acquires clock and data
within four bit times with an accuracy of ±3 ns
s Guaranteed carrier and collision detection
squelch threshold limits
— Carrier/collision detected for inputs greater than
–275 mV
— No carrier/collision for inputs less than –175 mV
GENERAL DESCRIPTION
The Am7992B Serial Interface Adapter (SIA) is a
Manchester encoder/decoder compatible with IEEE
802.3, Cheapernet, and Ethernet specifications. In an
IEEE 802.3/Ethernet application, the Am7992B inter-
faces the Am7990 Local Area Network Controller for
Ethernet (LANCE) to the Ethernet transceiver device,
BLOCK DIAGRAM
Receive Data (RX)
Receive Clock (RCLK)
Manchester
Decoder
s Input signal conditioning rejects transient noise
— Transients <10 ns for collision detector inputs
— Transients <20 ns for carrier detector inputs
s Receiver decodes Manchester data with worst
case ±19 ns of clock jitter (at 10 MHz)
s TTL-compatible host interface
s Transmit accuracy +0.01% (without adjustments)
acquires clock and data within four bit times, and de-
codes Manchester data with worst case ±19 ns phase
jitter at 10 MHz. SIA provides both guaranteed signal
threshold limits and transient noise suppression cir-
cuitry in both data and collision paths to minimize false
start conditions.
Data
Receiver
Receive+
Carrier Present (RENA)
Carrier
Detect
Noise
Reject
Filter
Receive–
Collision (CLSN)
Collision
Detect
Transmit Data (TX)
Transmit Enable (TENA)
Transmit Clock (TCLK)
20 MHz
Publication# 03378 Rev: I Amendment/0
Issue Date: May 1993
Manchester
Encoder
XTAL₁
Crystal
OSC
XTAL₂
Noise
Reject
Filter
Collision+
Collision–
Transmit+
Transmit–
03378I-1
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