Specifications

54
1
2345678PCM_OUT
PCM_CLK
PCM_SYNC
1
2345678
undefined
PCM_IN
1234
5
678
1234
5
678
undefined
Figure 30: 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.
PCM_OUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sign extension
8-bit sample
Figure 31: 16-bit slot with 8-bit companded sample and sign extension selected
PCM_OUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
8-bit sample
Zeros padding
Figure 32: 16-bit slot with 8-bit companded sample and zeros padding selected
PCM_OUT
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
3-bit sign
extension
13-bit sample
Figure 33: 16-bit slot with 13-bit linear sample and sign extension selected