Si3220/Si3225
CS
SCLK
SDI
CONTROL
ADDRESS
Data [15:8]
Data [7:0]
SDO
Figure 50. RAM Read Operation via a 16-Bit SPI Port
PCM Interface
The Dual ProSLIC devices contain
a
flexible duration of the 8-bit PCM transmit. DTX returns to high-
programmable interface for the transmission and impedance on the negative edge of PCLK during the
reception of digital PCM samples. PCM data transfer is LSB or on the positive edge of PCLK following the LSB.
controlled by the PCLK and FSYNC inputs, PCM Mode This is based on the setting of the PCMTRI bit of the
Select, PCM Transmit Start Count (PCMTXHI/ PCM Mode Select register. Tristating on the negative
PCMTXLO), and PCM Receive Start Count (PCMRXHI/ edge allows the transmission of data by multiple
PCMRXLO) registers. The interface can be configured sources in adjacent timeslots without the risk of driver
to support from 4 to 128 8-bit timeslots in each frame. contention. In addition to 8-bit data modes, a 16-bit
This corresponds to PCLK frequencies of 256 kHz to mode is provided for testing. This mode can be
8.192 MHz in power-of-2 increments. (768 kHz, activated via the PCMF bits of the PCM Mode Select
1.536 MHz, and 1.544 MHz are also available for T1 register.
Setting
the
PCMTXHI/PCMTXLO
or
and E1 support.) Timeslots for data transmission and PCMRXHI/PCMRXLO register greater than the number
reception are independently configured with the of PCLK cycles in a sample period stops data
PCMTXHI, PCMTXLO, PCMRXHI, and PCMRXLO. transmission because neither PCMTXHI/PCMTXLO nor
Setting the correct starting point of the data configures PCMRXHI/PCMRXLO equal the PCLK count. Figures
the part to support long FSYNC and short FSYNC 51–54 illustrate the usage of the PCM highway interface
variants, IDL2 8-bit, 10-bit, and B1 and B2 channel time to adapt to common PCM standards.
slots. DTX data is high-impedance except for the
PCLK
FSYNC
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
PCLK_CNT
DRX
MSB
MSB
LSB
LSB
DTX
HI-Z
HI-Z
Figure 51. Example, Timeslot 1, Short FSYNC (TXS/RXS = 1)
74
Rev. 1.0
SILICONIMAGE [ Silicon image ]
