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HFA3841 Datasheet(PDF) 16 Page - Intersil Corporation

Part No. HFA3841
Description  Wireless LAN Medium Access Controller
Download  27 Pages
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Maker  INTERSIL [Intersil Corporation]
Homepage  http://www.intersil.com/cda/home
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HFA3841 Datasheet(HTML) 16 Page - Intersil Corporation

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HFA3841 System Overview
External Memory Interface
An external memory space is provided for firmware and for
buffers that are used for temporary storage of received and
transmitted frames.
The total memory space is 4M bytes. 64K words are used for
control store, where firmware is located. The high data bus
has weak pull-up resistors so that external pull-down resistors
can set the configuration of the HFA3841 during reset.
NVCS- is the enable to the Flash memory device. Typically
the contents of the Flash are copied entirely into SRAM at
initialization, and then rarely if ever accessed during normal
operation. For this reason, it is acceptable to use low cost,
slow Flash devices. During initialization, the clock prescaler
is set to produce a longer cycle time while the Flash is
accessed. Once all the data has been copied, execution
jumps into SRAM and the clock is raised to the normal
operating frequency.
It is possible to operate without a Flash device. In such a
system, the firmware must be downloaded through the host
interface before operation can commence.
The external SRAM memory must be organized in a 16-bit
width to provide adequate performance to implement the
802.11 protocol at 11Mb/s rates. Systems designed for
lower performance applications may be able to use 8-bit
wide memory.
The minimum implementation of external memory consists
of 128K bytes of SRAM organized as 64K x 16. Typical
applications will use 256K bytes organized as 128K x 16. An
access point application could make use of the full address
space of the device with 4M bytes organized as 2M x 16.
FIGURE 13. TYPICAL APPLICATION
HFA3841
WIRELESS
MAC
CONTROLLER
PHY
TRANSCEIVER
HOST
INTERFACE
MAC
BRIDGE
HOST SYSTEM
(I/O DRIVER)
DISTRIBUTION
SYSTEM
I/O BUS
WIRELESS
MEDIUM
FOR ACCESS POINT
LAN
FOR STATION ADAPTER
FIGURE 14.
HFA3841
MD0..15
MA1..17
NVCS_
MOE_
MWEL_
MA0/MWEH_
RAMCS_
FLASH
128Kx8
MD0..7
MA0..16
CS_
OE_
SRAM
128Kx8
MD8..15
MA1..17
WE_
CS_
SPAM
128Kx8
MD0..7
MA1..17
OE_
CS_
WE_
OE_
Preliminary - HFA3841


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