BCM20705 Datasheet, PDF (30/67 Pages) Cypress Semiconductor – Single-Chip Bluetooth Transceiver and Baseband Processor

BCM20705 Data Sheet
PCM Interface
Slot Mapping
The device supports up to three simultaneous, full-duplex SCO or eSCO channels. These channels are time-
multiplexed onto the PCM interface using a time slotting scheme based on the audio sampling rate, as described
in Table 3.
Table 3: PCM Interface Time Slotting Scheme
Audio Sample Rate Time Slotting Scheme
8 kHz
The number of slots depends on the selected interface rate, as follows:
Interface rate Slot
128
1
256
2
512
4
1024
8
2048
16
16 kHz
The number of slots depends on the selected interface rate, as follows:
Interface rate Slot
256
1
512
2
1024
4
2048
8
Transmit and receive PCM data from an SCO channel is always mapped to the same slot. The PCM data output
driver tri-states its output on unused slots to allow other devices to share the same PCM interface signals. The
data output driver tri-states its output after the falling edge of the PCM clock during the last bit of the slot.
Wideband Speech
The BCM20705 provides support for Wideband Speech (WBS) in two ways:
• Transparent mode
The host encodes WBS packets and the encoded packets are
transferred over the PCM bus for SCO or eSCO voice connections.
In Transparent 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.
• On-chip SmartAudio® technology
The BCM20705 can perform Subband-Codec (SBC) encoding and
decoding of linear 16 bits at 16 kHz (256 kbps rate) transferred over
the PCM bus.
Broadcom®
Bluetooth Transceiver and Baseband Processor
November 13, 2014 • MCS20705-DS104-R
Page 29
BROADCOM CONFIDENTIAL