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
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)
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 interfaces the Am7990 Local Area Network Controller for
Ethernet (LANCE) to the Ethernet transceiver device,
acquires clock and data within four bit times, and decodes Manchester data with worst case ±19 ns phase
jitter at 10 MHz. SIA provides both guaranteed signal
threshold limits and transient noise suppression circuitry in both data and collision paths to minimize false
start conditions.
BLOCK DIAGRAM
Manchester
Decoder
Controller Interface
Collision (CLSN)
Noise
Reject
Filter
Receive–
Collision
Detect
Carrier Present (RENA)
Receive+
Carrier
Detect
Receive Clock (RCLK)
Data
Receiver
Noise
Reject
Filter
Collision+
Transmit Data (TX)
Manchester
Encoder
Transmit Enable (TENA)
Transmit Clock (TCLK)
Transmit–
Crystal
OSC
XTAL2
Amendment/0
Transmit+
XTAL1
20 MHz
Publication# 03378 Rev: I
Issue Date: May 1993
Collision–
Transceiver Interface
Receive Data (RX)
03378I-1
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