Production Data WM1824
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PD, Rev 4.1, December 2011
13
AUDIO DATA FORMATS
In Left Justified mode, the MSB is available on the first rising edge of BCLK following a
LRCLK transition. The other bits up to the LSB are then transmitted in order. Depending on
word length, BCLK frequency and sample rate, there may be unused BCLK cycles before
each LRCLK transition.
Figure 6 Left Justified Audio Interface (assuming n-bit word length)
In I
2
S mode, the MSB is available on the second rising edge of BCLK following a LRCLK
transition. The other bits up to the LSB are then transmitted in order. Depending on word
length, BCLK frequency and sample rate, there may be unused BCLK cycles between the
LSB of one sample and the MSB of the next.
Figure 7 I
2
S Justified Audio Interface (assuming n-bit word length)
DIGITAL AUDIO DATA SAMPLING RATES
The external master clock is applied directly to the MCLK input pin. In a system where there
are a number of possible sources for the reference clock, it is recommended that the clock
source with the lowest jitter be used for the master clock to optimise the performance of the
WM1824.
The WM1824 has a detection circuit that automatically determines the relationship between
the master clock frequency (MCLK) and the sampling rate (LRCLK), to within ±32 system
clock periods. The MCLK must be synchronised with the LRCLK, although the device is
tolerant of phase variations or jitter on the MCLK.
If during sample rate change the ratio between MCLK and LRCLK varies more than once
within 1026 LRCLK periods, then it is recommended that the device be taken into the standby
state or the off state before the sample rate change and held in standby until the sample rate
change is complete. This will ensure correct operation of the detection circuit on the return to
the enabled state. For details on the standby state, please refer to the Power up and down
control section of the datasheet on page 15.
