www.geehy.com Page 375
Figure 101 LSB Alignment Standard Waveform (24-bit data)
SPI_CK
Low
bit
Right channel
Left
channel
SPI_SD
High
bit
24-bit data
8-bit data is forced
to 0
SPI_WS
In the transmission process, if you want to transmit/receive 24-bit data, it is
required to read/write the SPI_DATA register twice; for example:
When you need to transmit 0x56EA98, write 0xXX56 to SPI_DATA
register for the first time, and write 0xEA98 to SPI_DATA for the
second time.
When you need to receive 0x56EA98, read out 0x0056 from
SPI_DATA registr for the first time, ad read out 0xEA98 from
SPI_DATA register for the second time.
In I2S configuration, when selecting the frame format of extending from 16-bit
data to 32-bit data frame, it is required to access SPI_DATA register, and the
high 16-bit data will be set to 0x0000 by hardware by forece; for example:
The data to be received or sent is 0x98A5, which becomes
0x000098A5 after it is expanded to 32 bits, and it is necessary to write
0x98A5 to SPI_DATA register or read out from SPI_DATA register.
Figure 102 Under LSB Alignment Standard (extending from 16 bits to 32 bits)
Low
bit
Right channel
Left
channel
SPI_SD
High
bit
16-bit data
16-bit data is
forced to 0
SPI_WS
SPI_CK
PCM standard
There is no sound channel selection in PCM standard. Short frame and long
frame of PCM standard are selected by configuring PFSSEL bit in SPI_I2SCFG
register.
In the master mode, the valid time of synchronous WS signal of the long frame