21 I
2
S
21-4
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
The sampling clock frequency is calculated as below.
f
I2S_SCLK
f
S
= ———— [Hz]
n
×
2
f
S
:
Sampling clock frequency [Hz]
f
I2S_SCLK
: Bit clock frequency [Hz] (See Table 21.4.2.)
n:
Number of bit clocks selected by WSCLKCYC[4:0] (See Table 21.4.3.)
Note: The value to be set to the WSCLKCYC[4:0] is not the number of audio data bits, but the number
of bit clock cycles that is used to adjust the sample clock period. It must be equal to or greater
than the number of audio data bits (16 bits).
1
2
3
15
16
17
n
1
2
3
D15
D2
D1
D0
D14
I2S_WS
I2S_SCLK
Bit clock cycle count
(by setting WSCLKCYC[4:0])
I2S_SDO
(L channel)
(R channel)
(MSB first, I
2
S mode)
D2
D15 D14
4.2 Sample Clock Period
Figure 21.
Selecting the word clock mode
The I2S_WS signal represents the current output channel (L or R) with its level (low or high).
Use WCLKMD/I2S_CTL register to select the relationship between the signal level and the L/R channel.
I2S_WS
WCLKMD = 0 (default)
(L channel)
(R channel)
I2S_WS
WCLKMD = 1
(L channel)
(R channel)
4.3 Word Clock Mode
Figure 21.
I2S_SCLK (bit clock) polarity
Use BCLKPOL/I2S_CTL register to select the bit clock polarity.
I2S_SCLK
I2S_SDO
BCLKPOL = 0 (default)
Data is shifted at the falling edge.
The external DAC samples the data at the rising edge.
I2S_SCLK
I2S_SDO
BCLKPOL = 1
Data is shifted at the rising edge.
The external DAC samples the data at the falling edge.
4.4 Bit Clock Polarity
Figure 21.
Setting the output data format and timing
Data format (MSB first/LSB first)
Use DTFORM/I2S_CTL register to select either MSB first or LSB first as the data output direction.
Setting DTFORM to 0 (default) selects MSB first and setting 1 selects LSB first.