參數(shù)資料
型號(hào): Am7968-175LKC
廠商: Advanced Micro Devices, Inc.
英文描述: TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
中文描述: TAXIchip集成電路(透明異步Xmitter,接收器接口)
文件頁(yè)數(shù): 101/127頁(yè)
文件大小: 730K
代理商: AM7968-175LKC
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AMD
97
TAXIchip Integrated Circuits Technical Manual
TAXI T
echnical
I
nformation
P
ublication
#89-03
S ubjec t: Proper Use for T AX I S ync
Question:
What is the proper use for Sync How often is a Sync needed
Answer:
When a Transmitter has no data to send, it sends Sync. This symbol allows the
Receiver PLL to maintain phase and frequency lock with the transmitter, exactly as
would a normal DATA stream. It has the additional special property of being a unique bit
pattern that can be used to discover the byte boundaries in an otherwise continuous
bit stream.
The Receiver PLL takes some time to achieve phase and frequency lock (as described
in section 3.3). After lock is achieved the TAXI Receiver must align the incoming data to
the proper byte boundaries. The Receiver logic compares the incoming bit stream (bit by
bit and without regard for byte boundaries) with the pattern for Sync, and when it is
found, forces an internal bit counter to 0 The internal counter then continues to count
bits and run the byte rate logic without further reference until another Sync is found.
From this description of the Sync function, it is obvious that only ONESync symbol is
ever really required to define the byte boundary for the TAXI Receiver if the internal
counter continues to count correctly. It is unlikely that the internal logic function will
make a mistake, and therefore the counter will continue to count off the proper number
of bits per byte forever. However, there is some chance that noise can corrupt DATA
into a pattern that looks exactly like the Sync symbol. (The chance is about 0.13% of all
possible error types.) When this happens, the byte boundary is forced to an incorrect
position, and all data following is decoded incorrectly. TAXI Receiver violation detection
logic may or may not flag the errors, but the Receiver cannot distinguish properly framed
data from incorrectly framed data. The only thing that can correct this running error is
another Sync.
The minimum number of Syncs required in a user data stream is dictated by the system
sensitivity to running errors, and the system’s built in error detection mechanism.
However, it is a good practice to send a Sync every 1000 bytes.
Systems that send packetizeddata, should allow a Sync between each packet. This will
assure that if an error occurs, it will be terminated at the end of the packet and will not
corrupt the succeeding packets. Systems that send data at a rate slower than the TAXI
byte rate will have Sync automatically inserted as pad characters, so the user may not
need to specifically insert them.
Systems that send byteor shortphrasedata (commands or control words, for example)
might send a Sync before each byteor phraseto assure that the message is not missed
because of an earlier framing error.
From this discussion it should be clear that there is no RIGHT NUMBER of Syncs to
send with TAXI data. The correct number is dependent on the type of data the user is
sending, and the system sensitivity to running errors.
相關(guān)PDF資料
PDF描述
Am7969-175LKC TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
AM7968-125VB3A TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AM7968-175LMC 制造商:AMD 制造商全稱(chēng):Advanced Micro Devices 功能描述:TAXIchip Integrated Circuits(Transparent Asynchronous Xmitter-Receiver Interface)
AM7968-175PC 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:Transmitter
AM7968-175PCB 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:Transmitter
AM7968-70/B3A 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:Transmitter
AM7968-70/BXA 制造商:未知廠家 制造商全稱(chēng):未知廠家 功能描述:Transmitter