BCM4390DKWBGT Datasheet, PDF (22/78 Pages) Cypress Semiconductor – WICED™ Wi-Fi IEEE 802.11 b/g/n SoC with Embedded Application Processor

BCM4390 Advance Data Sheet
Applications Microprocessor and Memory Unit
Section 4: Applications Microprocessor and
Memory Unit
The applications microprocessor core is based on the ARM® Cortex-M3™ 32-bit RISC processor with embedded
ICE-RT debug and JTAG interface units.
The applications processor boots from an internal ROM-based bootloader. The ROM bootloader copies a
configurable boot application from serial-flash to RAM, then passes execution to the boot application. The
applications processor is responsible for running the entirety of the WICED software stack, including the
optional RTOS, WLAN driver, various libraries to implement WLAN, networking features, and the end-user
application.
The 48 MHz processor operates efficiently in both power and performance with tightly-coupled SRAM of
448 KB to provide space for code execution and system resource and variable storage.
The application processor controls the peripheral I/O of the BCM4390, including a dedicated SPI flash interface,
SPI master/slave interface, GPIOs, I²C, I₂S, and four UARTs. The application processor is also responsible for
bootstrapping the WLAN core, including downloading the WLAN firmware from external serial flash storage.
The BCM4390 does not have internal flash storage: all code is stored and loaded from external serial flash.
In addition to the dedicated SPI interface to serial flash, the BCM4390 provides a secondary master/slave SPI
interface to allow expansion with other devices.
To reduce overall system power consumption, the application processor can be powered down independently
of the WLAN core. During powerdown, the state of the entire 448 KB of Applications RAM is retained.
Reset
The BCM4390 has an integrated power-on reset circuit that resets all circuits to a known power-on state. The
power-on reset (POR) circuit is out of reset after APPS_REG_ON goes High. If APPS_REG_ON is low, then the
POR circuit is held in reset.
BROADCOM ®
February 5, 2014 • 4390-DS103-R
WICED Wi-Fi IEEE 802.11 SoC w/Embedded App Processor
Page 21
BROADCOM CONFIDENTIAL