User's Manual

49
As with Long Frame Sync, WT32 samples PCM_IN on the falling edge of PCM_CLK and transmits
PCM_OUT on the rising edge. PCM_OUT may be configured to be high impedance on the falling edge
of PCM_CLK in the LSB position or on the rising edge.
7.4.4 Multi Slot Operation
More than one SCO connection over the PCM interface is supported using multiple slots. Up to three
SCO connections can be carried over any of the first four slots.
1
2 3 4 5 6 7 8PCM_OUT
PCM_CLK
LONG_PCM_SYNC
1
2 3 4 5 6 7 8
undefined undefined
PCM_IN
SHORT_PCM_SYNC
OR
Figure 28: Multi slot operation with two slots and 8-bit companded samples
7.4.5 GCI Interface
WT32 is compatible with the General Circuit Interface, a standard synchronous 2B+D ISDN timing
interface. The two 64Kbps B channels can be accessed when this mode is configured.
1
2 3 4 5 6 7 8PCM_OUT
PCM_CLK
PCM_SYNC
1
2 3 4 5 6 7 8
undefined
PCM_IN
1 2 3 4
5
6 7 8
1 2 3 4
5
6 7 8
undefined
Figure 29: GCI interface
The start of frame is indicated by the rising edge of PCM_SYNC and runs at 8kHz. With WT32 in Slave
mode, the frequency of PCM_CLK can be up to 4.096MHz.
7.4.6 Slots and Sample Formats
WT32 can receive and transmit on any selection of the first four slots following each sync pulse. Slot
durations can be either 8 or 16 clock cycles. Durations of 8 clock cycles may only be used with 8-bit
sample formats. Durations of 16 clocks may be used with 8, 13 or 16-bit sample formats.
WT32 supports 13-bit linear, 16-bit linear and 8-bit -law or A-law sample formats. The sample rate is
8ksamples/s. The bit order may be little or big Endian. When 16-bit slots are used, the 3 or 8 unused
bits in each slot may be filled with sign extension, padded with zeros or a programmable 3-bit audio
attenuation compatible with some Motorola CODECs.