BCM43236BKMLG Datasheet, PDF (17/43 Pages) Cypress Semiconductor – 2.4 GHz/5 GHz IEEE802.11n MAC/PHY/Radio Chip

BCM43236/BCM43236B Preliminary Data Sheet
IEEE 802.11n MAC Description
The MAC driver interacts with the MAC core to prepare queues of packets to transmit and to analyze and
forward received packets to upper software layers. The internal blocks of the MAC core are connected to a
Programmable State Machine (PSM) through the host interface that connects to the internal bus (see
Figure 6).
Figure 6: Enhanced MAC Block Diagram
TX Status FIFO
Power
Management
Timing and
Control
Host Interface
(Host Registers)
Six TX FIFOs
Template
RX FIFO
Wireless Security Engine
TX Engine
RX Engine
PHY Interface
Code Memory
Programmable
State Machine
(PSM)
Data Memory
The host interface consists of registers for controlling and monitoring the status of the MAC core and
interfacing with the TX/RX FIFOs. For transmit, a total of 128 KB FIFO buffering is available that can be
dynamically allocated to six transmit queues plus template space for beacons, ACKs, and probe responses.
Whenever the host has a frame to transmit, the host queues the frame into one of the transmit FIFOs with a
TX descriptor containing TX control information. The PSM schedules the transmission on the medium
depending on the frame type, transmission rules in IEEE 802.11 protocol, and the current medium occupancy
scenario. After the transmission is completed, a TX status is returned to the host, informing the host of the
result that got transmitted.
The MAC contains a single 10 KB RX FIFO. When a frame is received, it is sent to the host along with an RX
descriptor that contains additional information about the frame reception conditions.
The power management block maintains the information regarding the power management state of the core
(and the associated STAs in case of an AP) to help in dynamic decisions by the core regarding frame
transmission.
The wireless security engine performs the required encryption/decryption on the TX/RX frames. This block
supports separate transmit and receive keys with four shared keys and 50 link-specific keys. The link-specific
keys are used to establish a secure link between any two STAs, with the required key being shared between
only those two STAs, hence excluding all of the other STAs in the same network from deciphering the
communication between those two STAs. The wireless security engine supports the following encryption
schemes that can be selected on a per-destination basis:
• None: The wireless security engine acts as a pass-through
• WEP: 40-bit secure key and 24-bit IV as defined in IEEE Std. 802.11-2007
• WEP128: 104-bit secure key and 24-bit IV
• TKIP: IEEE Std. 802.11-2007
• AES: IEEE Std. 802.11-2007
BROADCOM ®
September 16, 2013 • 43236_43236B-DS103-R
Page 16