CYW4343X
10.1.4 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 CYW4343X 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.
10.1.5 Multiplexed Bluetooth and FM over PCM
In this mode of operation, the CYW4343X multiplexes both FM and Bluetooth audio PCM channels over the same interface, reduc-
ing the number of required I/Os. This mode of operation is initiated through an HCI command from the host. The data stream format
contains 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 Blue-
tooth 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 32 shows the operation of the multiplexed trans-
port 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 32. 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
BT SCO 3 TX
PCM_IN
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 3 times per frame.
Document No. 002-14797 Rev. *H
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