SLAS831 Data sheet

SLAS831D March 2014 – March 2018 PCM1860 , PCM1861 , PCM1862 , PCM1863 , PCM1864 , PCM1865

PRODUCTION DATA.

9.3.9.7 Clock Halt and Error Detect

The PCM186x has a clock error detection block inside that continues to monitor the ratio of BCK to LRCK.

If a clock error is detected (such as an unexpected number of BCKs per LRCK), then the device goes into standby mode.

If all the clocks are stopped going into the device, then the device shifts into sleep state, and begins Energysense signal detect mode.

When a clock error occurs, the PCM186x starts the following sequence:

Mute audio output immediately (without volume ramp down)
Wait until proper clock is supplied (known as Clock Waiting State)
Restart clock detection. The PLL and all clock dividers are reconfigured with the result of the detection.
Start fade-in

If the device stops transmitting data, the first step is to read CLK_ERR_STAT (Page.0 0x72). The least significant nibble shows the device status. Value 0x01 suggests Clock Waiting State, at which point the clock error status can be read in register STATE (Page.0 0x75). The clock detection logic is shown in Table 15.

Table 15. Summary of Clock Detection Logic

SCK	BCK	LRCK	RESULT	ACTION
ACTIVE	ACTIVE	ACTIVE	No error	Normal operation
ACTIVE	ACTIVE	HALT	Clock error	Enter clock waiting state
ACTIVE	HALT	ACTIVE	Clock error	Enter clock waiting state
ACTIVE	HALT	HALT	Clock error	Enter SLEEP
HALT	ACTIVE	ACTIVE	No error	Enter BCK PLL mode
HALT	ACTIVE	HALT	Clock error	Enter clock waiting state
HALT	HALT	ACTIVE	Clock error	Enter clock waiting state
HALT	HALT	HALT	Clock error	Enter SLEEP

In addition, the device uses an on-chip oscillator to detect errors in the rate of present clocks. That logic is shown in Table 16.

Table 16. Summary of Clock Error Logic

SCK/LRCK Ratio	BCK/LRCK RATIO	LRCK	ERROR DETECT	ACTION
-	-	< 8 kHz or > 192 kHz	f_S error	Enter clock waiting state
Not 128 / 256 / 384 / 512 / 768	-	8 / 16 / 32 / 44.1 / 48 kHz	SCK error	Enter the clock waiting state, tie I²S output to 0
Not 128 / 256 / 384 / 512	-	88.2 / 96 kHz	SCK error	Enter the clock waiting state, tie I²S output to 0
Not 128 / 256	-	176.4 / 192 kHz	SCK error	Enter the clock waiting state, tie I²S output to 0
	Not 256 / 64 / 48 / 32	8 / 16 / 32 / 44.1 / 48 / 88.2 / 96 / 174.6 / 196 kHz	BCK error	Enter the clock waiting state, tie I²S output to 0
		>192 kHz	f_S error	Enter the clock waiting state, tie I²S output to 0

In an application with a non-audio standard SCK coming into the product, the clock error detection on the SCK pin can be ignored by disabling the auto clock detector (CLKDET_EN Page.0 0x20).