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Nations Technologies Inc.
Tel
:
+86-755-86309900
:
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
Figure 21-22 LSB aligned 16-bit data is extended to 32-bit packet frame, CLKPOL = 0
If the 16-bit data needs to be packaged into a 32-bit data frame format, the CPU only needs to read or write the
SPI_DAT register once for each frame of data transmission. The upper 16 bits of extended to 32 bits data are set to
0x0000 by hardware, if the user sends or receives 16-bit data 0x89C1 (extended to 32-bit data is 0x000089C1). In
the process of sending data, the upper 16-bit halfword (0x0000) needs to be written to the SPI_DAT register first;
once the valid data starts to be send, the next TE (SPI_STS.TE) event will be generated. In the process of receiving
data, once the device receives valid data, the RNE (SPI_STS.RNE) event will be generated. In this way, there is more
time between 2 reads and writes, which can prevent underflow or overflow from happening.
PCM standard
In the PCM standard, there are two frame structures, short frame and long frame. The user can select the frame
structure by setting the SPI_I2SCFG.PCMFSYNC bits. The WS signal indicates frame synchronization information.
The WS signal for synchronizing long frames is 13 bits effective; the WS signal length for synchronizing short frames
is 1 bit.
The standard data receiving and sending processing mode is the same as I
2
S Philips standard.
CLK
WS
Send
Receive
SD
Left channel 32-bit
Right channel
LSB
16-bit data
16-bit data forced 0
MSB
MSB