BCM4339 Preliminary Data Sheet
Bluetooth Peripheral Transport Unit
Section 7: Bluetooth Peripheral Transport
Unit
SPI Interface
The BCM4339 supports a slave SPI HCI transport with an input clock range of up to 16 MHz. Higher clock rates
are possible. The physical interface between the SPI master and the BCM4339 contains the four SPI signals
(SPI_CSB, SPI_CLK, SPI_SI, and SPI_SO) and one interrupt signal (SPI_INT). The SPI signals are muxed onto
the UART signals, see Table 5. The BCM4339 can be configured to accept active-low or active-high polarity on
the SPI_CSB chip-select signal. It can also be configured to drive an active-low or active-high SPI_INT interrupt
signal. Bit ordering on the SPI_SI and SPI_SO data lines can be configured as either little-endian or big-endian.
Additionally, proprietary sleep mode and half-duplex handshaking is implemented between the SPI master and
the BCM4339. The SPI_INT is required to negotiate the start of a transaction. The SPI interface does not require
flow control in the middle of a payload. The FIFO is large enough to handle the largest packet size. Only the SPI
master can stop the flow of bytes on the data lines, since it controls SPI_CSB and SPI_CLK. Flow control should
be implemented in the higher layer protocols.
Table 5: SPI to UART Signal Mapping
SPI Signals
UART Signals
SPI_CLK
SPI_CSB
SPI_MISO
SPI_MOSI
SPI_INT
UART_CTS_N
UART_RTS_N
UART_RXD
UART_TXD
BT_HOST_WAKE
SPI/UART Transport Detection
The BT_HOST_WAKE (BT_GPIO1) pin is also used for BT transport detection. Transport detection occurs
during the power-up sequence. Either UART or SPI transport operation is selected based on the following pin
state:
•
If the BT_HOST_WAKE (BT_GPIO1) pin is pulled low by an external pull-down during power-up, the SPI
transport interface is selected.
•
If the BT_HOST_WAKE (BT_GPIO1) pin is not pulled low externally during power-up, then the default
internal pull-up is detected as a high and the UART transport interface is selected.
Broadcom®
November 17, 2014 • 4339-DS106-R
Page 48
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