CYW43340 datasheet(23/96 Pages) CYPRESS

23 / 96 page

Document Number: 002-14943 Rev. *L

Page 23 of 96

PRELIMINARY

CYW43340

7. Bluetooth Peripheral Transport Unit

7.1 PCM Interface

The CYW43340 supports two independent PCM interfaces that share the pins with the I2S interfaces. The PCM Interface on the

CYW43340 can connect to linear PCM Codec devices in master or slave mode. In master mode, the CYW43340 generates the

PCM_CLK and PCM_SYNC signals, and in slave mode, these signals are provided by another master on the PCM interface and are

inputs to the CYW43340. The configuration of the PCM interface may be adjusted by the host through the use of vendor-specific HCI

commands.

7.1.1 Slot Mapping

The CYW43340 supports up to three simultaneous full-duplex SCO or eSCO channels through the PCM interface. These three

channels are time-multiplexed onto the single PCM interface by using a time-slotting scheme where the 8 kHz or 16 kHz audio sample

interval is divided into as many as 16 slots. The number of slots is dependent on the selected interface rate of 128 kHz, 512 kHz, or

1024 kHz. The corresponding number of slots for these interface rate is 1, 2, 4, 8, and 16, respectively. Transmit and receive PCM

data from an SCO channel is always mapped to the same slot. The PCM data output driver tristates its output on unused slots to allow

other devices to share the same PCM interface signals. The data output driver tristates its output after the falling edge of the PCM

clock during the last bit of the slot.

7.1.2 Frame Synchronization

The CYW43340 supports both short- and long-frame synchronization in both master and slave modes. In short-frame synchronization

mode, the frame synchronization signal is an active-high pulse at the audio frame rate that is a single-bit period in width and is

synchronized to the rising edge of the bit clock. The PCM slave looks for a high on the falling edge of the bit clock and expects the

first bit of the first slot to start at the next rising edge of the clock. In long-frame synchronization mode, the frame synchronization

signal is again an active-high pulse at the audio frame rate; however, the duration is three bit periods and the pulse starts coincident

with the first bit of the first slot.

7.1.3 Data Formatting

The CYW43340 may be configured to generate and accept several different data formats. For conventional narrowband speech mode,

the CYW43340 uses 13 of the 16 bits in each PCM frame. The location and order of these 13 bits can be configured to support various

data formats on the PCM interface. The remaining three bits are ignored on the input and may be filled with 0s, 1s, a sign bit, or a

programmed value on the output. The default format is 13-bit 2’s complement data, left justified, and clocked MSB first.

7.1.4 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 CYW43340 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.

7.1.5 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.

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