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參數(shù)資料
| 型號(hào)： | AM79C970 |
| 廠商： | Advanced Micro Devices, Inc. |
| 英文描述： | PCnetTM-PCI Single-Chip Ethernet Controller for PCI Local Bus |
| 中文描述： | PCnetTM - PCI單芯片以太網(wǎng)控制器的PCI總線 |
| 文件頁數(shù)： | 56/168頁 |
| 文件大?。?/td> | 943K |
| 代理商： | AM79C970 |
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P R E L I M I N A R Y
AMD
1-923
Am79C970
Transmission is enabled by the controller. As long as the
ITXEN request remains active, the serial output of the
controller will be Manchester encoded and appear at
DO
±
. When the internal request is dropped by the con-
troller, the differential transmit outputs go to one of two
idle states, dependent on TSEL in the Mode Register
(CSR15, bit 9):
TSEL LOW:
The idle state of DO
±
yields “ZERO”
differential to operate transformer-
coupled loads.
TSEL HIGH: In this idle state, DO+ is positive with
respect to DO– (logical HIGH).
Receiver Path
The principal functions of the Receiver are to signal the
PCnet-PCI controller that there is information on the re-
ceive pair, and separate the incoming Manchester en-
coded data stream into clock and NRZ data.
The Receiver section (see Receiver Block Diagram)
consists of two parallel paths. The receive data path is a
ZERO threshold, wide bandwidth line receiver. The car-
rier path is an offset threshold bandpass detecting line
receiver. Both receivers share common bias networks
to allow operation over a wide input common
moderange.
18220C-26
Noise
Reject
Filter
Data
Receiver
Carrier
Detect
Circuit
Manchester
Decoder
IRXDAT*
ISRDCLK*
IRXCRS*
DI
±
*Internal signal
Figure 24
.
Receiver Block Diagram
Input Signal Conditioning
Transient noise pulses at the input data stream are re-
jected by the Noise Rejection Filter. Pulse width rejec-
tion is proportional to transmit data rate.
The Carrier Detection circuitry detects the presence of
an incoming data frame by discerning and rejecting
noise from expected Manchester data, and controls the
stop and start of the phase-lock loop during clock acqui-
sition. Clock acquisition requires a valid Manchester bit
pattern of 1010b to lock onto the incoming message.
When input amplitude and pulse width conditions are
met at DI
±
, the internal enable signal from the MENDEC
to controller (IRXCRS) is asserted and a clock acquisi-
tion cycle is initiated.
Clock Acquisition
When there is no activity at DI
±
(receiver is idle), the re-
ceive oscillator is phase locked to internal transmit
clock. The first negative clock transition (bit cell center of
first valid Manchester “0”) after IRXCRS is asserted in-
terrupts the receive oscillator. The oscillator is then re-
started at the second Manchester “0” (bit time 4) and is
phase locked to it. As a result, the MENDEC acquires
the clock from the incoming Manchester bit pattern in
4bit times with a 1010b Manchester bit pattern.
ISRDCLK and IRXDAT are enabled 1/4 bit time after
clock acquisition in bit cell 5. IRXDAT is at a HIGH state
when the receiver is idle (no ISRDCLK). IRXDAT how-
ever, is undefined when clock is acquired and may re-
main HIGH or change to LOW state whenever
ISRDCLK is enabled. At 1/4 bit time through bit cell 5,
the controller portion of the PCnet-PCI controller sees
the first ISRDCLK transition. This also strobes in the in-
coming fifth bit to the MENDEC as Manchester “1”.
IRXDAT may make a transition after the ISRDCLK rising
edge in bit cell 5, but its state is still undefined. The
Manchester “1” at bit 5 is clocked to IRXDAT output at
1/4 bit time in bit cell 6.
PLL Tracking
After clock acquisition, the phase-locked clock is com-
pared to the incoming transition at the bit cell center
(BCC) and the resulting phase error is applied to a cor-
rection circuit. This circuit ensures that the phase-
locked clock remains locked on the received signal.
Individual bit cell phase corrections of the Voltage Con-
trolled Oscillator (VCO) are limited to 100% of the phase
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AM79C970A | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product |
| AM79C970AKC | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet-PCI II Single-Chip Full-Duplex Ethernet Controller for PCI Local Bus Product |
| AM79C970AKC\\W | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Advanced Micro Devices 功能描述: |
| AM79C970AKC\W | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
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