BCM4354 Data Sheet
PCM Interface
Wideband Speech Support
When the host encodes Wideband Speech (WBS) packets in transparent mode, the encoded packets are
transferred over the PCM bus for an eSCO voice connection. In this mode, the PCM bus is typically configured
in master mode for a 4 kHz sync rate with 16-bit samples, resulting in a 64 Kbps bit rate. The BCM4354 also
supports slave transparent mode using a proprietary rate-matching scheme. In SBC-code mode, linear 16-bit
data at 16 kHz (256 Kbps rate) is transferred over the PCM bus.
Multiplexed Bluetooth and FM Over PCM
In this mode of operation, the BCM4354 multiplexes both FM and Bluetooth audio PCM channels over the same
interface, reducing the number of required I/Os. This mode of operation is initiated through an HCI command
from the host. The format of the data stream consists of three channels: a Bluetooth channel followed by two
FM channels (audio left and right). In this mode of operation, the bus data rate only supports 48 kHz operation
per channel with 16 bits sent for each channel. This is done to allow the low data rate Bluetooth data to coexist
in the same interface as the higher speed I2S data. To accomplish this, the Bluetooth data is repeated six times
for 8 kHz data and three times for 16 kHz data. An initial sync pulse on the PCM_SYNC line is used to indicate
the beginning of the frame.
To support multiple Bluetooth audio streams within the Bluetooth channel, both 16 kHz and 8 kHz streams can
be multiplexed. This mode of operation is only supported when the Bluetooth host is the master. Figure 9 shows
the operation of the multiplexed transport with three simultaneous SCO connections. To accommodate
additional SCO channels, the transport clock speed is increased. To change between modes of operation, the
transport must be halted and restarted in the new configuration.
Figure 9: Functional Multiplex Data Diagram
1 Frame
BT SCO 1 Rx
BT SCO 1 Tx
BT SCO 2 Rx
BT SCO 2 Tx
BT SCO 3 Rx
FM Right
FM Right
FM Left
FM Left
PCM_OUT
PCM_IN
BT SCO 3 Tx
PCM_SYNC
PCM_CLK
CLK
16 bits per SCO frame
16 bits per frame
16 bits per frame
Each SCO channel duplicates the data 6 times. Each WBS
frame duplicates the data three times per frame
Broadcom®
October 15, 2014 • 4354-DS109-R
Page 46
BROADCOM CONFIDENTIAL
CYPRESS [ CYPRESS ]
