PRELIMINARY
CYW43438
9. Microprocessor and Memory Unit for Bluetooth
The Bluetooth microprocessor core is based on the ARM Cortex-M3 32-bit RISC processor with embedded ICE-RT debug and JTAG
interface units. It runs software from the link control (LC) layer up to the host controller interface (HCI).
The ARM core is paired with a memory unit that contains 576 KB of ROM for program storage and boot ROM, and 160 KB of RAM
for data scratch-pad and patch RAM code. The internal ROM allows for flexibility during power-on reset (POR) to enable the same
device to be used in various configurations. At power-up, the lower-layer protocol stack is executed from the internal ROM memory.
External patches may be applied to the ROM-based firmware to provide flexibility for bug fixes or feature additions. These patches
may be downloaded from the host to the CYW43438 through the UART transports.
9.1 RAM, ROM, and Patch Memory
The CYW43438 Bluetooth core has 160 KB of internal RAM which is mapped between general purpose scratch-pad memory and
patch memory, and 576 KB of ROM used for the lower-layer protocol stack, test mode software, and boot ROM. The patch memory
is used for bug fixes and feature additions to ROM memory code.
9.2 Reset
The CYW43438 has an integrated power-on reset circuit that resets all circuits to a known power-on state. The BT POR circuit is out
of reset after BT_REG_ON goes high. If BT_REG_ON is low, then the POR circuit is held in reset.
Document Number: 002-14796 Rev. *K
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