ADM8211 IEEE 802.11b wireless network device
atw* at cardbus?
atw* at pci?
driver supports PCI/CardBus 802.11b
wireless adapters based on the ADMtek ADM8211.
The ADM8211 is a bus-mastering 802.11 Media Access Controller (MAC) which is
derived from ADMtek's DEC/Intel 21143 clones (see
for more information). It
supports contention-free traffic (with an 802.11 Point Coordinator). The
ADM8211 integrates an RF3000 baseband processor (BBP) by RF Microdevices.
In a typical application, the ADM8211 is coupled with an RF front-end by RFMD
and a Silicon Laboratories Si4126 RF/IF synthesizer.
With the ADM8211, the division of labor between the host and NIC is different
than with firmware-based NICs such as
. The ADM8211 is still
responsible for real-time 802.11 functions such as sending ACK/RTS/CTS/ATIM
frames, sending beacons, and answering CF polls from the access point, but the
host takes responsibility for providing 802.11 functions such as scanning,
association, and authentication. The host is also responsible for programming
both the BBP and the RF/IF synthesizer.
These are the modes the atw
driver can operate in:
- BSS mode
- Also known as infrastructure
mode, this is used when associating with an access point, through which
all traffic passes. This mode is the default.
- IBSS mode
- Also known as IEEE ad-hoc mode
or peer-to-peer mode. This is the
standardized method of operating without an access point. Stations
associate with a service set. However, actual connections between stations
driver can be configured to use hardware
Wired Equivalent Privacy (WEP) (though see
, below). It is strongly
recommended that WEP not be used as the sole mechanism to secure wireless
communication, due to serious weaknesses in it.
driver can be configured at runtime with
or on boot with
driver supports PCI and CardBus cards using
revisions 0x11 and 0x15 of the ADM8211 (aka ADM8211A) and revision 0x20 (aka
ADM8211B). This includes:
- 3Com OfficeConnect 3CRSHPW796 CardBus
- Belkin F5D6001 PCI (version 2 only)
- Blitz NetWave Point CardBus
- D-Link DWL-650 Rev. L1 CardBus
- D-Link DWL-520 Rev. C1 PCI
- LanReady WP2000 PCI
- SMC 2635W CardBus (version 1 only)
- TRENDnet TEW-221PC CardBus
- Xterasys XN2511B PCI
driver does not yet support cards using
revision 0x30 (ADM8211C).
The following example scans for available networks:
# ifconfig atw0 scan
The following hostname.if(5)
example configures atw0 to join network “mynwid”, using WEP key
“mywepkey”, obtaining an IP address using DHCP:
- atw0: failed to tune channel N
- The driver failed to tune the radio to a new channel. The
radio remains tuned to the old channel.
- atw0: atw_si4136_write wrote XXXX,
SYNCTL still busy
- The driver waited 100ms without seeing an indication that
the ADM8211 had finished writing a register on the Si4126 RF/IF
- atw0: device timeout
- The ADM8211 failed to generate an interrupt to acknowledge
a transmit command.
RF Micro Devices,
device driver first appeared in
driver was written by
For features which the ADM8211 has in common with the DECchip 21x4x, code was
liberally borrowed from the NetBSD
tlp driver by
The author does not fully understand what processing the duration fields for the
PLCP header and the 802.11 header undergo before they are applied to a
transmitted frame. If the duration fields in transmitted frames are incorrect,
network performance may suffer.
The driver does not provide rate control when the media type is set to
The driver will sometimes complain that it cannot re-tune the radio because the
transmit process has not gone idle. The author is investigating.
Many features are still missing, especially WEP decryption and 802.11
The ad-hoc mode has not been rigorously tested. IBSSs with the same SSID may not
coalesce, but this should not matter for most applications.
The driver is untested in the ad-hoc demo mode of Lucent WaveLAN cards.
The ADM8211 supports 802.11 power-saving; however,
does not support it yet. For time-bounded
service, the ADM8211 will interoperate with an access point which implements
the 802.11 Point Coordination Function; however, this is also not supported.
Combinations of an ADM8211 with either an Intersil or a Marvell RF front-end are
contains incomplete support for the ADM8211's
WEP encryption/decryption engine. atw
yet support hardware WEP decryption; however, it will use the ADM8211's crypto
engine to encrypt transmitted frames. Documentation from ADMtek claims that,
in addition to the 4 104-bit shared WEP keys, the ADM8211 will store WEP key
pairs for up to 20 peers. The documentation provides no details, hence
does not support the 20 key-pairs.