Serial peripheral interface / inter-IC sound (SPI/I2S)
RM0365
933/1080
DocID025202 Rev 7
Figure 361. Receiving 0x8EAA33
Figure 362. I
2
S Philips standard (16-bit extended to 32-bit packet frame)
When 16-bit data frame extended to 32-bit channel frame is selected during the I
2
S
configuration phase, only one access to the SPIx_DR register is required. The 16 remaining
bits are forced by hardware to 0x0000 to extend the data to 32-bit format.
If the data to transmit or the received data are 0x76A3 (0x76A30000 extended to 32-bit), the
operation shown in
is required.
Figure 363. Example of 16-bit data frame extended to 32-bit channel frame
For transmission, each time an MSB is written to SPIx_DR, the TXE flag is set and its
interrupt, if allowed, is generated to load the SPIx_DR register with the new value to send.
This takes place even if 0x0000 have not yet been sent because it is done by hardware.
For reception, the RXNE flag is set and its interrupt, if allowed, is generated when the first
16 MSB half-word is received.
In this way, more time is provided between two write or read operations, which prevents
underrun or overrun conditions (depending on the direction of the data transfer).
MSB justified standard
For this standard, the WS signal is generated at the same time as the first data bit, which is
the MSBit.
069
[($$
[;;
)LUVWUHDGWR'DWDUHJLVWHU
6HFRQGUHDGWR'DWDUHJLVWHU
2QO\WKH06%DUHVHQW
WRFRPSDUHWKHELWV
/6%VKDYHQRPHDQLQJ
DQGFDQEHDQ\WKLQJ
069
&.
:6
6'
7UDQVPLVVLRQ
5HFHSWLRQ
ELWGDWD
06%
/6%
&KDQQHOOHIWELW
&KDQQHOULJKW
ELWUHPDLQLQJIRUFHG
069
[$
2QO\RQHDFFHVVWR63,[B'5