BCM4354 datasheet(77/192 Pages) CYPRESS

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IEEE 802.11ac Draft MAC

BCM4354 Data Sheet

BROADCOM CONFIDENTIAL

Broadcom®

October 15, 2014 • 4354-DS109-R

Page 76

The BCM4354 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:

• Enhanced MAC for supporting IEEE 802.11ac Draft 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

• 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

• Hardware offload for AES-CCMP, legacy WPA TKIP, legacy WEP ciphers, WAPI, and support for key

management

• 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 scratchpad 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, scratchpad, IHRs, or instruction literals, and the results are written into the shared memory, scratchpad,

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.

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