CYW43362
8. WLAN Software Architecture
8.1 Host Software Architecture
The host driver (DHD) provides a transparent connection between the host operating system and the CYW43362 media (for exam-
ple, WLAN) by presenting a network driver interface to the host operating system and communicating with the CYW43362 over an
interface-specific bus (SPI, SDIO, and so on) to:
■
Forward transmit and receive frames between the host network stack and the CYW43362 device, and
Pass control requests from the host to the CYW43362 device, returning the CYW43362 device responses
■
The driver communicates with the CYW43362 over the bus using a control channel and a data channel to pass control messages
and data messages. The actual message format is based on the BDC protocol.
8.2 Device Software Architecture
The wireless device, protocol, and bus drivers are run on the embedded ARM® processor using a Cypress-defined operating sys-
tem called HNDRTE, which transfers data over a propriety Cypress format over the SDIO/SPI interface between the host and device
(BDC/LMAC). The data portion of the format consists of IEEE 802.11 frames wrapped in a Cypress encapsulation. The host side
architecture provides all missing functionality between a network device and the Cypress device interface. The host can also be cus-
tomized to provide functionality between the Cypress device interface and a full network device interface.
This transfer requires a message-oriented (framed) interconnect between the host and device. The SDIO bus is an addressed bus—
each host-initiated bus operation contains an explicit device target address—and does not natively support a higher-level data frame
concept. Cypress has implemented a hardware/software message encapsulation scheme that ignores the bus operation code
address and prefixes each frame with a 4-byte length tag for framing. The device presents a packet-level interface over which data,
control, and asynchronous event (from the device) packets are supported.
The data and control packets received from the bus are initially processed by the bus driver and then passed on to the protocol
driver. If the packets are data packets, they are transferred to the wireless device driver (and out through its medium), and a data
packet received from the device medium follows the same path in the reverse direction. If the packets are control packets, the proto-
col header is decoded by the protocol driver. If the packets are wireless IOCTL packets, the IOCTL API of the wireless driver is
called to configure the wireless device. The microcode running in the D11 core processes all time-critical tasks.
8.2.1 Remote Downloader
When the CYW43362 powers up, the DHD initializes and downloads the firmware to run in the device.
Figure 21. WLAN Software Architecture
DHD Host Driver
SPI/SDIO
BDC/LMAC Protocol
Wireless Device Driver
D11 Core
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