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HFA3842B Datasheet(PDF) 14 Page - Intersil Corporation

Part No. HFA3842B
Description  PCMCIA/USB Wireless LAN Medium Access Controller
Download  26 Pages
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Maker  INTERSIL [Intersil Corporation]
Homepage  http://www.intersil.com/cda/home
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HFA3842B Datasheet(HTML) 14 Page - Intersil Corporation

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14
External Memory Interface
The HFA3842B provides separate external chip selects for
code space and data storage space. Code space is
accessible as data space through an overlay mechanism,
except for an internal ROM. Refer to Figures 12, 13 and 14
for HFA3842B memory configuration details. Refer to
Figure 15 for memory map.
The maximum possible memory space size is 4Mbytes. If
USB is the host interface, this is reduced to 1Mbyte.
Most of the data store space is reserved for storage of
received and transmitted data, with some areas reserved for
use by firmware. However, a portion of the data store may be
allocated as code store. This permits higher speed
instruction execution, by using fast RAMs, than is possible
from Flash memories. The maximum size of this overlay is
the full code space address range, 128Kbytes, and is
allocated in independent sections of 16KBytes each, on
16Kbyte boundaries, ranging from the highest address of the
actual physical memory space and extending down.
Mapping code execution to RAM requires the RAM to have
code written into it. Typically, this is done by placing code in a
non-volatile memory such as a Flash in the code space. At
initialization, the code in the non-volatile memory transfers itself
DS ADDR
(BYTE)
0x0
3FF
400
DATA STORE MAP
AFTER
HARDWARE RESET
DATA STORE MAP
GENERIC
EXT RAM SPACE
400
TO
7EFFFF
DATA SPACE
400
TO
NV ADDRESSES
RANGE FROM
TOP OF
DATA SPACE
DOWN
PHY ADDRESSES
RANGE FROM
TOP OF DATA
SPACE DOWN AND
OVERLAY NV
RANGE. AFFECTS
MOPs ONLY
INTERNAL DS
1KBYTES
ORGANIZED
512x16, BYTE
ACCESS
WEP USES
0x200-0x3FF
WEP USES
0x200-0x3FF
ICS ROM 512 WORDS
NV SPACE
32KB
ICS RAM 8KB
ICS
ICS ROM 512 WORDS
RAM
8KB
PHY
SPACE
7E0000
7E03FF
7F8000
7FE000
7FFFFF
FFFF
1FFFF
3FFFF
7FFFF
FFFFF
1FFFFF
3FFFFF
7FFFFF
RAM SPACE SIZES
400000
200000
100000
80000
40000
20000
10000
8000
NV SPACE SIZES
4000
1000
400
100
40
NV
SPACE
INTERNAL DS
1KBYTES
ORGANIZED
512x16, BYTE
ACCESS
FIGURE 15. MEMORY MAP
RAM SIZE = 0
RAM SIZE = 1
RAM SIZE = 2
RAM SIZE = 3
RAM SIZE = 4
RAM SIZE = 5
RAM SIZE = 6
RAM SIZE = 7
64KB
128KB
256KB
512KB
1MB
2MB
4MB
8MB
NV SIZE = 7
NV SIZE = 6
NV SIZE = 5
NV SIZE = 4
NV SIZE = 3
NV SIZE = 2
NV SIZE = 1
NV SIZE = 0
4096KB
2048KB
1024KB
512KB
256KB
128KB
64KB
32KB
HFA3842B


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