BCM43455 Preliminary 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 BCM43455 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 Over PCM
Bluetooth supports multiple audio streams within the Bluetooth channel and 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 10
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 10: 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
PCM_OUT
PCM_IN
BT SCO 3 Tx
PCM_SYNC
PCM_CLK
CLK
16 bits per SCO frame
Each SCO channel duplicates the data 6 times. Each
WBS frame duplicates the data 3 times per frame
Burst PCM Mode
In this mode of operation, the PCM bus runs at a significantly higher rate of operation to allow the host to duty
cycle its operation and save current. In this mode of operation, the PCM bus can operate at a rate of up to
24 MHz. This mode of operation is initiated with an HCI command from the host.
Broadcom®
November 5, 2015 • 43455-DS109-R
Page 49
BROADCOM CONFIDENTIAL
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