User Manual

DS656F3 49

CS4245

shown in Table 18. The volume changes are implemented as dictated by the DACSoft and DACZero-

Cross bits in the DAC Control 2 register (see Section 6.12.1).

6.12 DAC Control 2 - Address 0Ch

6.12.1 DAC Soft Ramp or Zero Cross Enable (Bits 7:6)

Function:

Soft Ramp Enable

Soft Ramp allows level changes, both muting and attenuation, to be implemented by incrementally ramp-

ing, in 1/8 dB steps, from the current level to the new level at a rate of 1 dB per 8 left/right clock periods.

See Table 19.

Zero Cross Enable

Zero Cross Enable dictates that signal-level changes, either by attenuation changes or muting, will occur

on a signal zero crossing to minimize audible artifacts. The requested level change will occur after a time-

out period between 512 and 1024 sample periods (10.7 ms to 21.3 ms at 48 kHz sample rate) if the signal

does not encounter a zero crossing. The zero cross function is independently monitored and implemented

for each channel. See Table 19.

Soft Ramp and Zero Cross Enable

Soft Ramp and Zero Cross Enable dictate that signal-level changes, either by attenuation changes or mut-

ing, will occur in 1/8 dB steps and be implemented on a signal zero crossing. The 1/8 dB level change will

occur after a time-out period between 512 and 1024 sample periods (10.7 ms to 21.3 ms at 48 kHz sam-

ple rate) if the signal does not encounter a zero crossing. The zero cross function is independently mon-

itored and implemented for each channel. See Table 19.

6.12.2 Invert DAC Output (Bit 5)

Function:

When this bit is set, the output of the DAC is inverted.

Binary Code Volume Setting

00000000 0 dB

00000001 -0.5 dB

00101000 -20 dB

00101001 -20.5 dB

11111110 -127 dB

11111111 -127.5 dB

Table 18. Digital Volume Control Example Settings

76543210

DACSoft DACZero InvertDAC Reserved Reserved Reserved Reserved Active_H/L

DACSoft DACZeroCross Mode

0 0 Changes to affect immediately

0 1 Zero Cross enabled

1 0 Soft Ramp enabled

1 1 Soft Ramp and Zero Cross enabled (default)

Table 19. DAC Soft Cross or Zero Cross Mode Selection