CS8920A View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS8920A' PDF : 144 Pages View PDF
CS8920A
10BASE-T Only: When configured for 10BASE-
T-only operation, the 10BASE-T transceiver and
its interface to the ENDEC are active, and the
AUI is powered down.
AUI Only: When configured for AUI-only opera-
tion, the AUI and its interface to the ENDEC are
active, and the 10BASE-T transceiver is powered
down.
Auto-Select: In Auto-Select mode, the CS8920A
automatically selects the 10BASE-T interface
and powers down the AUI if valid packets or link
pulses are detected by the 10BASE-T receiver. If
valid packets and link pulses are not detected,
the CS8920A selects the AUI. Whenever the AUI
is selected, the 10BASE-T receiver remains ac-
tive to listen for link pulses or packets. If
10BASE-T activity is detected, the CS8920A
switches back to 10BASE-T.
3.12 10BASE-T Transceiver
The CS8920A includes an integrated 10BASE-T
transceiver that is compliant with the relevant
portions of section 14 of the Ethernet standard
(ISO/IEC 8802-3, 1993). It includes all analog
and digital circuitry needed to interface the
CS8920A directly to a simple isolation trans-
former (see section 11.0 for a connection
diagram). Figure 3.10 provides a block diagram
of the 10BASE-T transceiver.
10BASE-T Filters
The CS8920A’s 10BASE-T transceiver includes
integrated low-pass transmit and receive filters,
eliminating the need for external filters or a fil-
ter/transformer hybrid. On-chip filters are gm/c
implementations of fifth-order Butterworth low-
pass filters. Internal tuning circuits keep the
gm/c ratio tightly controlled, even when large
temperature, supply, and IC process variations
LinkOK
(to MAC)
ENDEC
RXSQL
RX
TX
10BASE-T Transceiver
Link Pulse
Detector
RX Squelch
RX
Comparator
RX Filters
TX Pre-
Distortion
TX Filters
Filter Tuning
TX Drivers
RXD-
RXD+
TXD-
TXD+
Figure 3.10. 10BASE-T Transceiver
34
DS238PP2
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