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參數(shù)資料
| 型號： | AM79C901AVI |
| 廠商： | ADVANCED MICRO DEVICES INC |
| 元件分類： | 網(wǎng)絡(luò)接口 |
| 英文描述： | HomePHY Single-Chip 1/10 Mbps Home Networking PHY |
| 中文描述： | DATACOM, ETHERNET TRANSCEIVER, PQFP80 |
| 封裝： | PLASTIC, MO-136BAM, TQFP-80 |
| 文件頁數(shù)： | 34/90頁 |
| 文件大?。?/td> | 714K |
| 代理商： | AM79C901AVI |
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34
Am79C901A
P R E L I M I N A R Y
The next two AID symbols (5 and 6) encode four bits
of control word information. The MSB is encoded in
AID Symbol 5. Control word messages are described
further in the
Mode Interface
section.
AID Transmit Timing
: The transmitter encodes the Ac-
cess ID in a pulse position in each 129 TIC interval.
Each AID symbol interval must have only one pulse.
Pulse transmission must start in only one of the four
possible positions (measured from the beginning of the
Access ID symbol) defined in Table 7.
AID Receive Timing
: The receiver allows for jitter by
establishing a window around each legal pulse posi-
tion. This asymmetrical window is two TICS wide on
one side of the position and one TIC wide on the other.
A pulse that arrives outside of the legal AID positions is
considered a COLLISION event.
Collisions
A Collision is detected only during Access ID and silent
intervals (AID symbols 0 through 7). In general during
a collision, a transmitting station will read back an AID
value that does not match its own, recognize the event
as a collision, and alert other stations with a JAM sig-
nal. Non-transmitting stations may also detect some
collisions by interpreting received non-conforming AID
pulses as collisions.
With two transmitters colliding, each transmitter nor-
mally blanks its receive input immediately after trans-
mitting (and simultaneously receiving) a pulse.
Therefore, only when a transmitting station receives
pulses in a position earlier than the position it transmit-
ted will it recognize it as a pulse transmitted by another
station and signal a collision.
For this reason, guaranteed collision detection is pos-
sible only as long as the spacing between successive
possible pulse positions in an AID symbol (20 TICs or
2.3
μ
s) is greater than the roundtrip delay between the
colliding nodes. At approximately 1.5 ns propagation
delay per foot, the maximum distance between two
HomePNA units must not be greater than 500 feet for
collision detection purposes (1.5
μ
s roundtrip delay
plus margin).
The following criteria must be met to guarantee reliable
collision detection:
At least one HomePNA station of a colliding group must
always detect a collision when the delay between the
beginning of its transmitted packet and the beginning of
the received colliding packet is between -1.5
μ
s and
+1.5
μ
s.
In general, any received pulse at a HomePNA station
that does not conform to the pulse position require-
ments of AID symbols 0 through 7 shall indicate a col-
lision on the wire. When a transmitting station senses
a collision, it emits a JAM signal to alert all other sta-
tions to the collision. The following conditions signify
a COLLISION event:
1. A HomePNA station receives an AID that does not
match the one being sent.
2. A HomePNA station receives a pulse outside the
AID_GUARD INTERVAL in AID intervals 0 to 7.
3. A HomePNA station receives a pulse inside the
SILENT_INTERVAL (AID symbol 7).
As in all cases, pulses received during a blanking
interval are ignored.
Passive stations (stations not actively transmitting dur-
ing the collision) cannot reliably detect collisions.
Therefore, once a collision is detected by a transmitting
station, the station must inform the rest of the stations
of the collision with a JAM pattern described below.
Only a transmitting station emits a JAM signal.
Once a collision is detected, the COLLISION signal to
the MAC interface is asserted and is not reset until the
MAC deactivates the TXEN signal.
JAM Signal
A JAM pattern consists of 1 pulse every 32 TICs and
continues until at least the end of the AID intervals.
After the AID interval, the JAM pattern will continue
until TXEN from the MAC is deactivated.
Access ID Values
The access ID values for stations are randomly picked
by each individual station from the set of AID numbers
described in the management section. During opera-
tion, each HomePNA station monitors HomePNA
frames received on the wire. If it detects another Home-
PNA station using the same AID, it will select a new
random AID.
Silence Interval (AID symbol 7)
The Access ID symbols are followed by a fixed silence
interval of 129 TICs. The receive blanking interval is the
same as that of the AID symbols (1 through 6).
Any pulses detected in the silence interval are consid-
ered a COLLISION event for transmitting stations and
are handled as described in the
Collisions
section.
Data Symbols
Data symbols encode data for a much higher transmis-
sion rate, and they do not allow collision detection.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AM79C901AVIT | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:HomePHY Single-Chip 1/10 Mbps Home Networking PHY |
| AM79C90JC | 制造商:Rochester Electronics LLC 功能描述: |
| AM79C90JC-G | 制造商:Rochester Electronics LLC 功能描述: |
| AM79C90JCTR | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:CMOS Local Area Network Controller for Ethernet (C-LANCE) |
| AM79C90PC | 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:CMOS Local Area Network Controller for Ethernet (C-LANCE) |
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