Cirrus Logic CS4391A - Manual (Page 19)

CS4391A
DS600PP3 19
4.2 VOLUME AND MIXING CONTROL (ADDRESS 02H)
4.2.1 Channel A Volume = Channel B Volume (Bit 7)
Function:
The AOUTA and AOUTB volume levels are independently controlled by the A and the B Channel Vol-
ume Control Bytes when this function is disabled. The volume on both AOUTA and AOUTB are de-
termined by the A Channel Volume Control Byte and the B Channel Byte is ignored when this function
is enabled.
4.2.2 Soft Ramp or Zero Cross Enable (Bits 6:5)
Function:
Soft Ramp Enable
Soft Ramp allows level changes, both muting and attenuation, to be implemented by incrementally
ramping, in 1/8 dB steps, from the current level to the new level at a rate of 1dB per 8 left/right clock
periods.
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 timeout 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 mon-
itored and implemented for each channel.
Soft Ramp and Zero Cross Enable
Soft Ramp and Zero Cross Enable dictates that signal level changes, either by attenuation changes
or muting, 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 timeout 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 5
4.2.3 ATAPI Channel Mixing and Muting (Bits 4:0)
Function:
The CS4391A implements the channel mixing functions of the ATAPI CD-ROM specification.
See Table 6
4.3 CHANNEL A VOLUME CONTROL - ADDRESS 03H
See Section 4.4 Channel B Volume Control - Address 04h
7 6 5 4 3 2 1 0
A = B Soft Zero Cross ATAPI4 ATAPI3 ATAPI2 ATAPI1 ATAPI0