參數(shù)資料
型號(hào): AM79C875KI
廠商: ADVANCED MICRO DEVICES INC
元件分類: 網(wǎng)絡(luò)接口
英文描述: NetPHY⑩ 4LP Low Power Quad 10/100-TX/FX Ethernet Transceiver
中文描述: DATACOM, ETHERNET TRANSCEIVER, PQFP100
封裝: 14 X 20 MM, PLASTIC, QFP-100
文件頁(yè)數(shù): 13/48頁(yè)
文件大?。?/td> 2480K
代理商: AM79C875KI
Am79C875
13
FUNCTIONAL DESCRIPTION
Overview
The NetPHY 4LP transceiver is a four-port CMOS
device that implements the complete physical layer for
10BASE-T and the Physical Coding Sublayer (PCS),
Physical Medium Attachment (PMA), and Physical Me-
dium Dependent (PMD) functionality for 100BASE-TX.
The NetPHY 4LP transceiver implements Auto-Ne-
gotiation allowing two devices connected across a link
segment to take maximum advantage of their capabili-
ties. Auto-Negotiation is performed as defined in the
IEEE 802.3u specification.
The NetPHY 4LP device communicates with a
switch or MAC device through the Reduced Media In-
dependent Interface (RMII).
The NetPHY 4LP device consists of the following
functional blocks:
RMII Functional Blocks
100BASE-X Block including:
— Transmit and Receive State Machines
— 4B/5B Encoder and Decoder
— Stream Cipher Scrambler and Descrambler
— Link Monitor State Machine
— Far End Fault Indication (FEFI) State Machine
— MLT-3 Encoder
— MLT-3 Decoder with adaptive equalization
10BASE-T Block including:
— Manchester Encoder/Decoder
— Jabber
— Receive Polarity Detect
— Waveshaping and Filtering
Carrier Integrity Monitor
Auto-Negotiation
Status LEDs
PHY Control and Management
Modes of Operation
The RMII interface provides the data path connection
between the NetPHY 4LP transceivers and the
Media Access Controller (MAC), repeater, or switch de-
vices. The MDC and MDIO pins are responsible for
communication between the NetPHY 4LP trans-
ceiver and the station management entity (STA).
The RMII standard reduces the pin count by halving the
number of data pins, eliminating pins not used in switch
applications, and using a single global clock. Each port
has an independent RMII.
RMII uses seven pins per port. They are as follows:
Receive Data
RXD[X]_[1:0]
Carrier Sense
CRS_DV[X]
Receive Error
RX_ER[X]
Transmit Data
TXD[X]_[1:0]
Transmit Enable
TX_EN[X]
Note:
[X] refers to the port.
In RMII mode, REF_CLK must be sourced by a
50-MHz clock signal.
RMII Pin Descriptions
CRS_DV
Carrier Sense/Receive Data Valid
CRS_DV is asserted by the PHY when the receive me-
dium is non-idle. Loss of carrier results in the deasser-
tion of CRS_DV synchronous to the cycle of REF_CLK,
which presents the first di-bit of a nibble onto RXD[1:0]
(i.e., CRS_DV is deasserted only on nibble bound-
aries). If the PHY has additional bits to be presented on
RXD[1:0] following the initial deassertion of CRS_DV,
the PHY asserts CRS_DV on cycles of REF_CLK
which present the second di-bit of each nibble. The
PHY deasserts CRS_DV on cycles of REF_CLK which
present the first di-bit of the nibble. As a result, starting
on the byte boundaries, CRS_DV toggles at 25 MHz in
100 Mbps mode and 2.5 MHz in 10 Mbps mode when
CRS ends before RX_DV (i.e., the FIFO still has bits to
transfer when the carrier event ends). Therefore, the
MAC can accurately recover RX_DV and CRS. Refer
to Figure 1.
During a false carrier event, CRS_DV remains as-
serted for the duration of carrier activity. Refer to
Figure 2.
The data on RXD[1:0] is considered valid once
CRS_DV is asserted. However, since the assertion of
CRS_DV is asynchronous relative to REF_CLK, the
data on RXD[1:0] is “00” until proper receive signal
decoding takes place.
Note:
CRS_DV is asserted asynchronously in order
to minimize latency of control signals through the PHY.
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