參數(shù)資料
型號： 91C94
廠商： SMSC Corporation
英文描述： ISA/PCMCIA SINGLE CHIP ETHERNET CONTROLLER WITH RAM
中文描述： 的ISA / PCMCIA的單芯片以太網(wǎng)控制器與RAM
文件頁數(shù)： 84/120頁
文件大?。?/td> 447K
代理商： 91C94
66
THEORY OF OPERATION
The concept of presenting the shared RAM as a
FIFO of packets, with a memory management
unit allocating memory on a per packet basis
responds to the following needs:
Memory allocation for receive vs. transmit - A
fixed partition between receive and transmit area
would
not
be
efficient.
Being
able
to
dynamically allocate it to transmit and receive
represents almost the equivalent of duplicating
the memory size for some workstation type of
drivers.
Software overhead - By presenting a FIFO of
packets, the software driver does not have to
waste any time in calculating pointers for the
different buffers that make up different packets.
The driver usually deals with one packet at a
time.
With
this
approach,
packets
are
accessible always at the same fixed address,
and access is provided to any byte of the
packet.
Headers can be analyzed without reading out
the entire packet. The packet can be moved in
or out with a block move operation.
Multiple upper layer support - The LAN91C94
facilitates interfacing to multiple upper layer
protocols
because
of
the
receive
packet
processing flexibility.
A receive lookahead
scheme like ODI or NDIS drivers is supported
by copying a small part of the received packet
and letting the upper layer provide a pointer for
the rest of the data. If the upper layer indicates
it does not want the packet, it can be removed
upon a single command.
If the upper layer
wants a specific part of the packet, a block
move operation starting at any particular offset
can be done. Out of order receive processing is
also supported: if memory for one packet is not
yet available, receive packet processing can
continue.
Efficiency - Lacking any level of indirection or
linked lists of pointers, virtually all the memory
is used for data.
There are no descriptors,
forward links and pointers at all. This simplicity
and memory efficiency is accomplished without
giving up the benefits of linked lists which is
unlimited
back-to-back
transmission
and
reception without CPU intervention for as long
as memory is available.
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
91CCC3 制造商:Wirepro 功能描述:Connector Accessories Cap and Chain For Receptacle
91-CCC3 制造商:CDM ELECTRONIC FORMERLY WPI 功能描述:connector accessory,circular microphone,cap and chain for receptacle
91-CCC-3 制造商:Amphenol Corporation 功能描述: 制造商:TE Connectivity 功能描述:
91CR10 制造商:TT Electronics / BI Technologies 功能描述:Res Cermet Trimmer 10 Ohm 20% 1/2W 1(Elec)/1(Mech)Turn (9.53 X 9.78 X 7.11mm) Pin Thru-Hole Box
91CR100 功能描述:微調(diào)電阻 - 通孔 3/8inch 100 Thumbwheel RoHS:否 制造商:Vishay/Sfernice 產(chǎn)品:Trimmer Resistors - Multi Turn 產(chǎn)品類型:Multiturn 轉(zhuǎn)數(shù):14 錐度:Linear 電阻:10 kOhms 電壓額定值:250 V 端接類型:Pin 功率額定值:250 mW (1/4 W) 容差:10 % 溫度系數(shù):100 PPM / C
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