Specifications

Si3216
Rev. 1.0 49
Not Recommended
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2.10. PCM Interface
The ProSLIC contains a flexible programmable interface
for the transmission and reception of digital PCM
samples. PCM data transfer is controlled via the PCLK
and FSYNC inputs as well as the PCM Mode Select
(direct Register 1), PCM Transmit Start Count (direct
registers 2 and 3), and PCM Receive Start Count (direct
registers 4 and 5) registers. The interface can be
configured to support from 2 to 64 16-bit timeslots in
each frame. This corresponds to PCLK frequencies of
256 kHz to 8.192 MHz in power-of-2 increments.
(768 kHz and 1.536 MHz are also available.) Timeslots
for data transmission and reception are independently
configured using the TXS and RXS registers. For the
Si3216 in wideband mode (WBE = 1, PCMF = 11, and
PCMT = 1), TXS and RXS set the correct starting point
of the data for the first timeslot within the 8 kHz frame,
and the second timeslot is set to follow 62.5 µs later.
Figure 29 illustrates the use of the PCM in wideband
mode. DTX data is high-impedance except for the
duration of the 16-bit PCM transmit. DTX returns to
high-impedance either on the negative edge of PCLK
during the LSB or on the positive edge of PCLK
following the LSB. This is based on the setting of the
TRI bit of the PCM Mode Select register. Tristating on
the negative edge allows the transmission of data by
multiple sources in adjacent timeslots without the risk of
driver contention. GCI timing is also supported in which
the duration of a data bit is two PCLK cycles. This mode
is also activated via the PCM Mode Select register.
Setting the TXS or RXS register greater than the
number of PCLK cycles in a sample period stops data
transmission because TXS or RXS never equals the
PCLK count.
Figure 29. Wideband PCM Operation Example, Short FSYNC, PCLK = 512 kHz (TXS/RXS = 1)
Bit
15
Bit
14
MSB LSB
HI-Z
Bit
1
Bit
0
01 171632494835343318
63
MSB LSB
HI-Z
Bit
1
Bit
0
Bit
15
Bit
14
Bit
15
Bit
14
Bit
1
Bit
0
Bit
15
Bit
14
MSB LSB
HI-Z
Bit
1
Bit
0
PCLK
FSYNC
PCLK_CNT
DRX
DTX
01