ISD94100 Series Technical Reference Manual
Sep 9, 2019
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I2S_BCLK cycle of an audio channel. The MSB justified and LSB justified data format of I
2
S protocol
can be selected by FORMAT (I2S_CTL0[26:24]).
I2S_BCLK
I2S_LRCLK
I2S_DI /
I2S_DO
Data width
Data width
Left channel of frame N
Right channel of frame N
Left channel
of frame N+1
LSB MSB
MSB
LSB
MSB
Figure 6.17-7 I
2
S Data Format Timing Diagram (FORMAT = 0x0 ; CHWIDTH
≦
DATWIDTH)
MSB
I2S_BCLK
I2S_LRCLK
I2S_DI /
I2S_DO
Redundant
Zero Pad
Redundant
Zero Pad
Data width
Data width
LSB
MSB
MSB
LSB
Left channel of frame N
Right channel of frame N
Left channel
of frame N+1
…
…
Figure 6.17-8 MSB Justified Data Format (FORMAT = 0x1 ; CHWIDTH > DATWIDTH)
MSB
I2S_BCLK
I2S_LRCLK
I2S_DI /
I2S_DO
Redundant
Zero Pad
Redundant
Zero Pad
Data width
Data width
LSB
MSB
MSB
LSB
Left channel of frame N
Right channel of frame N
Left channel
of frame N+1
Redundant
Zero Pad
…
…
Figure 6.17-9 LSB Justified Data Format (FORMAT = 0x2 ; CHWIDTH > DATWIDTH)
The I
2
S controller also supports PCM audio transmission which can be selected by FORMAT
(I2S_CTL0[26:24]). In PCM protocol, the function of I2S_LRCLK is simply to identify the beginning
of an audio sample (or audio frame) and it is always indicated by the rising edge of the pulse.
Therefore, the I2S_LRCLK in PCM protocol may be also called “frame start” or “frame sync” signal.
In master device, there are two common representations for the width of the frame start pulse which
can use PCMSYNC (I2S_CTL0[27]) to choose: One is equivalent to the period of a channel width
and the other is equivalent to a single period of the I2S_BCLK.
Same as I
2
S protocol, the DATWIDTH (I2S_CTL0[5:4]) and CHWIDTH (I2S_CTL0[29:28]) can be
used to configure the data bit-width and channel bit-width in PCM protocol. Besides, FORMAT
(I2S_CTL0[26:24]) can also be used to select the different data formats of PCM standard mode,
