BCM88335 Data Sheet
IEEE 802.11ac MAC
The BCM88335 WLAN media access controller (MAC) supports features specified in the IEEE 802.11 base
standard, and amended by IEEE 802.11n. The key MAC features include:
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Enhanced MAC for supporting IEEE 802.11ac features
Transmission and reception of aggregated MPDUs (A-MPDU) for high throughput (HT)
Support for power management schemes, including WMM power-save, power-save multi-poll (PSMP) and
multiphase PSMP operation
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Support for immediate ACK and Block-ACK policies
Interframe space timing support, including RIFS
Support for RTS/CTS and CTS-to-self frame sequences for protecting frame exchanges
Back-off counters in hardware for supporting multiple priorities as specified in the WMM specification
Timing synchronization function (TSF), network allocation vector (NAV) maintenance, and target beacon
transmission time (TBTT) generation in hardware
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Hardware offload for AES-CCMP, legacy WPA TKIP, legacy WEP ciphers, WAPI, and support for key
management
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Support for coexistence with Bluetooth and other external radios
Programmable independent basic service set (IBSS) or infrastructure basic service set functionality
Statistics counters for MIB support
PSM
The programmable state machine (PSM) is a micro-coded engine, which provides most of the low-level control
to the hardware, to implement the IEEE 802.11 specification. It is a microcontroller that is highly optimized for
flow control operations, which are predominant in implementations of communication protocols. The instruction
set and fundamental operations are simple and general, which allows algorithms to be optimized until very late
in the design process. It also allows for changes to the algorithms to track evolving IEEE 802.11 specifications.
The PSM fetches instructions from the microcode memory. It uses the shared memory to obtain operands for
instructions, as a data store, and to exchange data between both the host and the MAC data pipeline (via the
SHM bus). The PSM also uses a scratch-pad memory (similar to a register bank) to store frequently accessed
and temporary variables.
The PSM exercises fine-grained control over the hardware engines, by programming internal hardware registers
(IHR). These IHRs are co-located with the hardware functions they control, and are accessed by the PSM via
the IHR bus.
The PSM fetches instructions from the microcode memory using an address determined by the program
counter, instruction literal, or a program stack. For ALU operations the operands are obtained from shared
memory, scratch-pad, IHRs, or instruction literals, and the results are written into the shared memory, scratch-
pad, or IHRs.
There are two basic branch instructions: conditional branches and ALU based branches. To better support the
many decision points in the IEEE 802.11 algorithms, branches can depend on either a readily available signals
from the hardware modules (branch condition signals are available to the PSM without polling the IHRs), or on
the results of ALU operations.
Broadcom®
September 23, 2015 • 88335-DS100-R
Page 67
BROADCOM CONFIDENTIAL
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