Specifications

GOODOCOM Technologies Confidential GOC-BA440 Specification
GOODOCOM Technologies Confidential 21
11. PCM Interface
The PCM Interface on the GOC-BA440 can connect to linear PCM Codec devices in master or slave
mode. In master mode,the GOC-BA440 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 GOC-BA440.
The configuration of the PCM interface may be adjusted by the host through the use of vendor-specific
HCI commands.
Slot Mapping
The GOC-BA440 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.
Frame Synchronization
The GOC-BA440 supports both short- and long-frame synchronization in both master and slave
modes. In shortframe 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.
Data Formatting
The GOC-BA440 may be configured to generate and accept several different data formats. For
conventional narrowband speech mode, the GOC-BA440 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.