PCM1794A
ZHCSEE9B –AUGUST 2004–REVISED DECEMBER 2015
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7.3.3 Audio Data Interface
7.3.3.1 Audio Serial Interface
The audio interface port is a 3-wire serial port that includes LRCK (pin 4), BCK (pin 6), and DATA (pin 5). BCK is
the serial audio bit clock, and used to clock the serial data present on DATA into the serial shift register of the
audio interface. Serial data is clocked into the PCM1794A device on the rising edge of BCK. LRCK is the serial
audio left/right word clock.
The PCM1794A device requires the synchronization of LRCK and the system clock, but does not require a
specific phase relation between LRCK and the system clock.
If the relationship between LRCK and the system clock changes more than ±6 BCK, internal operation is
initialized within 1/fS, and the analog outputs are forced to the bipolar zero level until resynchronization between
LRCK and the system clock is completed.
7.3.3.2 PCM Audio Data Formats and Timing
The PCM1794A device supports industry-standard audio data formats, including standard right-justified, I2S, and
left-justified. The data formats are shown in Figure 22. Data formats are selected using the format bits, FMT1
(pin 12), and FMT0 (pin 11) as shown in Table 3. All formats require binary twos-complement, MSB-first audio
data. The Timing Requirements table lists and Figure 3 shows a detailed timing diagram for the serial audio
interface.
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