PRELIMINARY
CYW43438
10.1.5 Multiplexed Bluetooth and FM over PCM
In this mode of operation, the CYW43438 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 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. 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 22 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 22. 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 Number: 002-14796 Rev. *K
Page 41 of 101
CYPRESS [ CYPRESS ]
