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參數(shù)資料
| 型號： | AM79C873 |
| 廠商： | Advanced Micro Devices, Inc. |
| 英文描述： | NetPHY⑩ -1 10/100 Mbps Ethernet Physical Layer Single-Chip Transceiver with 100BASE-FX Support |
| 中文描述： | NetPHY⑩-1 10/100 Mbps以太網(wǎng)物理層的單芯片收發(fā)器與100BASE - FX的支持 |
| 文件頁數(shù)： | 15/44頁 |
| 文件大?。?/td> | 543K |
| 代理商： | AM79C873 |
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Am79C873
15
P R E L I M I N A R Y
Table 1.
4B5B Code Group
Scrambler
The scrambler is required to control the radiated emis-
sions (EMI) by spreading the transmit energy across
the frequency spectrum at the media connector and on
the twisted pair cable in 100BASE-TX operation. By
scrambling the data, the total energy presented to the
cable is randomly distributed over a wide frequency
range. Without the scrambler, energy levels on the
cable could peak beyond FCC limitations at frequen-
cies related to repeated 5B sequences like continuous
transmission of IDLE symbols. The scrambler output is
combined with the NRZ 5B data from the code-group
encoder via an XOR logic function. The result is a
scrambled data stream with sufficient randomization to
decrease radiated emissions at critical frequencies.
Since EMI is not a concern in a fiber application, the
scrambler is bypassed in 100BASE-FX.
Parallel-to-Serial Converter
The Parallel-to-Serial Converter receives parallel 5B
scrambled data from the scrambler and serializes it
(i.e., converts it from a parallel to a serial data stream).
The serialized data stream is then presented to the
NRZ-to-NRZI Encoder block
NRZ-to-NRZI Converter
After the transmit data stream has been scrambled and
serialized, the data must be NRZI encoded for compati-
bility with the TP-PMD standard for 100BASE-TX trans-
mission over Category-5 unshielded twisted pair cable.
PECL Driver For 100BASE-FX
The PECL driver accepts NRZI coded data and converts
it to PECL signal levels for transmission over fiber media.
The output pair is a differential pseudo ECL (PECL) in-
terface designed to connect directly to a standard fiber
optic PMD. The differential driver for the FXTD± is cur-
rent mode and is designed to drive resistive termination
in a complementary mode. The FXTD± pins are inca-
pable of sourcing current, this implies that VOH must
be set by the ratios of the Thevenin termination resis-
tors for each of the lines. RIOH is a pull-up resistor con-
nected from the FXTD± output to VCC. RIOL is a pull-
down resistor connected from the FXTD± output to
ground. RIOH and RIOL are electrically in parallel from
an AC standpoint. A target impedance of 50
is
needed for the transmission line impedance. A value of
62
for RIOH and a value of 300
for RIOL will yield
a Thevenin equivalent characteristic impedance of
49.7
and a VOH value of VCC-.88 volts, compatible
with PECL circuits. VOL is required to be VDD-1.81 or
greater. A sink current of 19 milli-amps (mA) would
achieve this through the output termination resistors.
MLT-3 Converter
The MLT-3 conversion is accomplished by converting the
data stream output from the NRZI encoder into two bi-
nary data streams with alternately phased logic
one events.
Symbol
Meaning
4B code
3210
5B Code
43210
0
Data 0
0000
11110
1
Data 1
0001
01001
2
Data 2
0010
10100
3
Data 3
0011
10101
4
Data 4
0100
01010
5
Data 5
0101
01011
6
Data 6
0110
01110
7
Data 7
0111
01111
8
Data 8
1000
10010
9
Data 9
1001
10011
A
Data A
1010
10110
B
Data B
1011
10111
C
Data C
1100
11010
D
Data D
1101
11011
E
Data E
1110
11100
F
Data F
1111
11101
I
Idle
undefined
11111
J
SFD (1)
0101
11000
K
SFD (2)
0101
10001
T
ESD (1)
undefined
01101
R
ESD (2)
undefined
00111
H
Error
undefined
00100
V
Invalid
undefined
00000
V
Invalid
undefined
00001
V
Invalid
undefined
00010
V
Invalid
undefined
00011
V
Invalid
undefined
00101
V
Invalid
undefined
00110
V
Invalid
undefined
01000
V
Invalid
undefined
01100
V
Invalid
undefined
10000
V
Invalid
undefined
11001
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相關(guān)代理商/技術(shù)參數(shù) |
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| AM79C873KCW | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:NetPHY⑩ -1 10/100 Mbps Ethernet Physical Layer Single-Chip Transceiver with 100BASE-FX Support |
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| AM79C874KC/W | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LAN Transceiver |
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