8.1 MAC

The ATWILC3000-MR110xA module is designed to operate at low power, while providing high data throughput. The IEEE 802.11 MAC functions are implemented with a combination of dedicated datapath engines, hardwired control logic and a low power, high-efficiency microprocessor. The combination of dedicated logic with a programmable processor provides optimal power efficiency and real-time response while providing the flexibility to accommodate evolving standards and future feature enhancements.

The dedicated datapath engines are used to implement datapath functions with heavy computational requirements. For example, a Frame Check Sequence (FCS) engine checks the Cyclic Redundancy Check (CRC) of the transmitting and receiving packets and a cipher engine performs all the required encryption and decryption operations for the WEP, WPA-TKIP, WPA2 CCMP-AES and WPA2 Enterprise security requirements.

Control functions, which have real-time requirements, are implemented using hardwired control logic modules. These logic modules offer a real-time response while maintaining configurability through the processor. Examples of hardwired control logic modules are the channel access control module (implements EDCA, Beacon TX control, interframe spacing and so on), protocol timer module (responsible for the Network Access vector, back-off timing, timing synchronization function and slot management), MAC Protocol Data Unit (MPDU) handling module, aggregation/deaggregation module, block ACK controller (implements the protocol requirements for burst block communication) and TX/RX control Finite State Machine (FSM) (coordinates data movement between PHY and MAC interface, cipher engine and the Direct Memory Access (DMA) interface to the TX/RX FIFOs).

The following are the characteristics of the MAC functions implemented solely in the software on the microprocessor:

• Functions with high memory requirements or complex data structures. Examples include association table management and power save queuing.
• Functions with low computational load or without critical real-time requirements. Examples include authentication and association.
• Functions that require flexibility and upgradeability. Examples include beacon frame processing and QoS scheduling.