User's Manual

Silicon Laboratories Finland Oy
Page 37 of 51
Figure 31: GCI Interface
The start of frame is indicated by the rising edge of PCM_SYNC and runs at 8kHz. With WT11u in Slave mode,
the frequency of PCM_CLK can be up to 4.096MHz.
9.6 Slots and Sample Formats
WT11u 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-bit, 13-bit or 16-bit sample formats.
WT11u 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.