BCM20705 Datasheet, PDF (31/67 Pages) Cypress Semiconductor – Single-Chip Bluetooth Transceiver and Baseband Processor

BCM20705 Data Sheet
HCI Transport Detection Configuration
Frame Synchronization
The device supports both short and long frame synchronization types in both master and slave configurations.
In short frame synchronization mode, the frame synchronization signal is an active-high pulse at the 8 kHz audio
frame rate (which is a single bit period in width) and synchronized to the rising edge of the bit clock. The PCM
slave expects PCM_SYNC to be high on the falling edge of the bit clock and the first bit of the first slot to start
at the next rising edge of the clock. In the long frame synchronization mode, the frame synchronization signal
is an active-high pulse at the 8 kHz audio frame rate. However, the duration is 3-bit periods and the pulse starts
coincident with the first bit of the first slot.
Data Formatting
The device can be configured to generate and accept several different data formats. The device uses 13 of the
16 bits in each PCM frame. The location and order of these 13 bits is configurable to support various data
formats on the PCM interface. The remaining three bits are ignored on the input, and may be filled with zeros,
ones, a sign bit, or a programmed value on the output. The default format is 13-bit two’s complement data, left
justified, and clocked most significant bit first.
HCI Transport Detection Configuration
The BCM20705 supports the following interface types for the HCI transport from the host:
• UART (H4 and H5)
• USB
• SPI
Only one host interface can be active at a time. The firmware performs a transport detect function at boot-time
to determine which host is the active transport. It can auto-detect UART and USB interfaces, but the SPI
interface must be selected by strapping the SCL pin to 0.
The complete algorithm is summarized as follows:
1. Determine if SCL is pulled low. If it is, select SPI as HCI host transport.
2. Determine if any local NVRAM contains a valid configuration file. If it does and a transport configuration entry
is present, select the active transport according to entry, and then exit the transport detection routine.
3. Look for start-of-frame (SOF) on the USB interface. If it is present, select USB.
4. Look for CTS_N = 0 on the UART interface. If it is present, select UART.
5. Repeat Step 3 and Step 4 until transport is determined.
Broadcom®
Bluetooth Transceiver and Baseband Processor
November 13, 2014 • MCS20705-DS104-R
Page 30
BROADCOM CONFIDENTIAL