Cirrus Logic CS42L73 - Manual (Page 55)

DS882F1 55
CS42L73
4.8.6.1 I²S Format
Selecting I²S format provides the following behavior:
• Up to 24 bits/sample of stereo data can be transported (see “Data Bit Depths” on page 57 )
• Master or Slave timing may be selected
• xSP_LRCK identifies the start of a new sample word and the active stereo channel (A or B)
• Data is clocked into the xSP_SDIN input using the rising edge of xSP_SCLK
• Data is clocked out of the xSP_SDOUT output using the falling edge of xSP_SCLK
• Bit order is MSB to LSB
Refer to section “Mono/Stereo” on page 57 for details on how the stereo nature of the I²S format impacts
the operation of the VSP.
The signaling for I²S format is shown in Figure 27 .
4.8.6.2 PCM Format
If PCM format is selected:
• 16 bits/sample of mono data can be transported (refer to “Data Bit Depths” on page 57 )
• Slave timing is supported
• xSP_LRCK (aka WA) identifies the start of a new sample word, acting as a Word-Aligner
• Data is clocked into the xSP_SDIN input using the falling edge of xSP_SCLK
• Data is clocked out of the xSP_SDOUT output using the rising edge of xSP_SCLK
• Bit order may selected as MSB-to-LSB or LSB-to-MSB
• The PCM Mode must be selected
PCM Format supports word bit-order reversal (LSB-to-MSB vs. MSB-to-LSB) via the XPCM_BIT_ORDER
and VPCM_BIT_ORDER bits. If enabled, the data in the location (refer to the signaling waveforms in
Figures 28 to 30 ) normally occupied by the data’s MSB bit is occupied by the data’s LSB bit, the location
normally occupied by the data’s MSB-1 bit is occupied by the data’s LSB+1 bit, and so on.
The X_PCM_MODE[1:0] and V_PCM_MODE[1:0] fields select how WA (xSP_LRCK) may vary in width
and location vs. the data.
Mode 0:
– WA may be one or two xSP_SCLK periods wide
– 1st data bit is transported in the cycle following WA
– No data is sampled into the CS42L73 during WA
– When WA is 2 xSP_SCLK periods wide, the first data bit is output from the CS42L73 for 2 cycles,
during the last active cycle of WA and during the bit that follows WA (as usual)
Section “Mono/Stereo” on page 57 describes how the mono nature of the PCM format affects operation.
Signaling for all PCM format modes, with xPCM_BIT_ORDER = 0b (MSB-to-LSB), are shown in
Figures 28 to 30 ).
Figure 27. I²S Format
xSP_LRCK
xSP_SCLK
xSP_SDIN
xSP_SDOUT
MSB MSB-1 LSB+1 LSB
1/Fs
ext
Note:
x = X, A, or V
MSB MSB-1 LSB+1 LSB MSB
xSP_SCLK may
stop or continue
t
extraA =
None to some time
xSP_SCLK may
stop or continue
t
extraB =
None to some time
Left (A) Channel Right (B) Channel