User manual

...the world's most energy friendly microcontrollers
2012-04-24 - Giant Gecko Family - d0053_Rev0.96 466
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The regular I2S waveform is shown in Figure 17.16 (p. 466) and Figure 17.17 (p. 466) . The first
figure shows a waveform transmitted with full accuracy. The wordlength can be configured to 32-bit,
16-bit or 8-bit using FORMAT in USARTn_I2SCTRL. In the second figure, I2S data is transmitted with
reduced accuracy, i.e. the data transmitted has less bits than what is possible in the bus format.
Note that the msb of a word transmitted in regular I2S mode is delayed by one cycle with respect to
word select
Figure 17.16. USART Standard I2S waveform
USn_CLK
USn_CS
(word select)
USn_TX/
USn_RX
MSB
Left channelRight channel Right channel
LSB MSBLSB
Figure 17.17. USART Standard I2S waveform (reduced accuracy)
USn_CLK
USn_CS
(word select)
USn_TX/
USn_RX
MSB
Left channelRight channel Right channel
LSB MSB
A left-justified stream is shown in Figure 17.18 (p. 466) . Note that the MSB comes directly after the
edge on the word-select signal in contradiction to the regular I2S waveform where it comes one bit-
period after.
Figure 17.18. USART Left-justified I2S waveform
USn_CLK
USn_CS
(word select)
USn_TX/
USn_RX
MSB
Left channelRight channel Right channel
LSB MSB
A right-justified stream is shown in Figure 17.19 (p. 467) . The left and right justified streams are equal
when the data-size is equal to the word-width.