CS8920A View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS8920A' PDF : 144 Pages View PDF
CS8920A
LINKLED or HC0: LINKLED or HC0 can be
controlled by either the CS8920A or the host.
When controlled by the CS8920A, LINKLED is
low whenever the CS8920A receives valid
10BASE-T link pulses. To configure this pin for
CS8920A control, the HC0E bit (Register 15,
SelfCTL, Bit C) must be clear. When controlled
by the host, LINKLED is low whenever the
HCB0 bit (Register 15, SelfCTL, Bit E) is set.
To configure it for host control, the HC0E bit
must be set. Table 3.9 summarizes this operation.
BSTATUS or HC1: BSTATUS or HC1 can be
controlled by either the CS8920A or the host.
When controlled by the CS8920A, BSTATUS is
low whenever the host reads the RxEvent regis-
ter (PacketPage base + 0124h), signaling the
transfer of a receive frame across the ISA bus.
To configure this pin for CS8920A control, the
HC1E bit (Register 15, SelfCTL, Bit D) must be
clear. When controlled by the host, BSTATUS is
low whenever the HCB1 bit (Register 15,
SelfCTL, Bit F) is set. To configure it for host
control, HC1E must be set. Table 3.10 summa-
rizes this operation.
+5V
LOCALLED
LANLED
LOCALLED: LOCALLED goes low whenever
local LAN activity is occurring. Local LAN ac-
tivity is defined as either the the receipt of
Ethernet frames that pass the address filter of
the CS8920A, or the transmission of frames onto
the Ethernet. This LED is intended to be used
on the front panel of a PC in a manner analo-
gous to a Hard Drive Activity LED. See Section
5.3 for discussion of the receive address filter.
LED Connection
Each LED output is capable of sinking 10 mA to
drive an LED directly through a series resistor.
The output voltage of each pin is less than 0.4 V
when the pin is low. Figure 3.4 shows a typical
LED circuit.
3.10 Media Access Control
Overview
The CS8920A’s Ethernet Media Access Control
(MAC) engine is fully compliant with the IEEE
802.3 Ethernet standard (ISO/IEC 8802-3, 1993).
It handles all aspects of Ethernet frame transmis-
sion and reception, including: collision detection,
preamble generation and detection, and CRC
generation and test. Programmable MAC fea-
tures include automatic retransmission on
collision, and padding of transmitted frames.
Figure 3.5 shows how the MAC engine inter-
faces to other CS8920A functions. On the host
side, it interfaces to the CS8920A’s internal
LED
Logic
LINKLED
Figure 3.4. LED Connection Diagram
CS8920A
Internal Bus
802.3
MAC
Engine
Figure 3.5. MAC Interface
Encoder/
Decoder
&
PLL
10BASE-T
& AUI
DS238PP2
27
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