WM8728

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WOLFSON MICROELECTRONICS LTD

PP Rev 1.2 April 2001

15

HARDWARE DSD MODE

DSD mode is selected by taking the SCKDSD pin high whilst the MODE pin is low. In this mode

the internal digital filters are bypassed, and the already modulated bitstream data is applied

directly to the Switched Capacitor DAC filter where it is converted and lowpass filtered, see Figure

26 to Figure 29.

Two formats are supported for data transfer, MONOPHASE or BIPHASE MODULATED.

In Monophase mode, DSD data is simply clocked into the device using the rising edge of the 64fs

MCLK signal.

In Biphase mode, the data is supplied in Manchester encoded form (a bit transition occurs during

every data bit, which shapes the spectral energy minimising corruption of the analogue outputs).

A secondary clock BCKIN, at 128fs is used to simplify data recovery, the data simply being

clocked with the falling edge of BCKIN when MCLK is at logic low (0V).

See Figure 3 and Figure 4 for details of DSD interface timing.

HARDWARE CONTROL MODES

When the MODE pin is held low, the following hardware modes of operation are available.

MUTE AND AUTOMUTE OPERATION

In both hardware and software modes, pin 17 (MUTEB) controls the selection of MUTE directly,

and can be used to enable and disable the automute function. This pin becomes an output when

left floating and indicates infinite ZERO detect (IZD) see also pin 5 (ZERO).

MUTEB PIN

DESCRIPTION

0

Mute DAC channels

1

Normal Operation

Floating

Enable IZD, MUTEB becomes an output to indicate when IZD occurs.

L=IZD detected, H=IZD not detected.

Table 2 Mute and Automute Control

Figure 12 shows the application and release of MUTE whilst a full amplitude sinusoid is being

played at 48kHz sampling rate. When MUTE (lower trace) is asserted, the output (upper trace)

begins to decay exponentially from the DC level of the last input sample. The output will decay

asserted, the output will restart almost immediately from the current input sample.

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

0

0.001

0.002

0.003

0.004

0.005

0.006

Time(s)