Serial Bus Analysis
R&S
®
RTM3000
307
User Manual 1335.9090.02 ─ 08
TDM uses frame synchronization pulses on the WS line to identify the beginning of
a frame.
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The data line transmits the audio data in time-multiplexed data channels.
12.7.1.1
I²S Standard
I²S standard interfaces transmit two PCM coded audio channels. The WS line selects
the channel being transmitted - left or right channel. Usually, 32 bits are transmitted on
each channel. The data word can be shorter than the channel length, and the receiver
ignores the remaining bits. The first byte of the audio word is delayed one clock period
from the leading edge of the word select pulse. The R&S
RTM3000 can decode I²S
standard signals with MSBF and LSBF bit order.
12.7.1.2
Left Justified Data Format
The left justified data format is very similar to the I²S standard, but the first byte of the
audio word is aligned with the leading edge of the word select pulse. Thus the audio
word is left justified within the frame. The data word can be shorter than the channel
length.
In addition to the standard configuration, the R&S
RTM3000 can analyze also left justi-
fied data formats which send the data word with offset to the WS edge. The bit order
can be MSBF or LSBF.
12.7.1.3
Right Justified Data Format
The right-justified data format is similar to the left-justified, but the last byte of the word
in the frame is aligned with the trailing edge of the word select pulse. Thus the audio
word is right-aligned within the frame.
12.7.1.4
TDM
The Time Division Multiplexed (TDM) audio format is not standardized and provides
high flexibility for transfer of more than two audio data channels on one line. On the
word select line, it uses frame synchronization pulses to identify the beginning of a
Audio Signals (Option R&S
RTM-K5)
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