Cirrus Logic CS42L56 - Manual (Page 45)

DS851F2 45
CS42L56
4.7 Limiter
When enabled, the limiter monitors the digital input signal before the DAC modulators, detects when levels
exceed the maximum threshold settings and lowers the master volume at a programmable attack rate below
the maximum threshold. When the input signal level falls below the maximum threshold, the AOUT volume
returns to its original level set in the Master Volume Control register at a programmable release rate. Attack
and release rates are affected by the DAC soft ramp settings and sample rate, Fs. Limiter soft ramp depen-
dency may be independently enabled/disabled using the LIMSRDIS.
It should be noted that the Limiter maintains the output signal between the CUSH and MAX thresholds. As
the digital input signal level changes, the level-controlled output may not always be the same but will always
fall within the thresholds
Recommended settings: Best limiting performance may be realized with a fast attack and a slow release
setting with soft ramp enabled in the control registers. The CUSH bits allow the user to set a threshold slight-
ly below the maximum threshold for hysteresis control - this cushions the sound as the limiter attacks and
releases.
Referenced Control Register Location
MSTxVOL[7:0].....................
PMIXxVOL[6:0]....................
OFFTIME[2:0]......................
ONTIME[3:0] .......................
FREQ[3:0] ...........................
BEEP[1:0]............................
BPVOL[4:0] ......................... “Master Volume Control: MSTA (Address 13h) & MSTB (Address 14h)” on page 70
“PCMx Mixer Volume: PCMA (Address 0Fh) & PCMB (Address 10h)” on page 68
“Beep Off Time” on page 71
“Beep On Time” on page 71
“Beep Frequency” on page 70
“Beep Configuration” on page 72
“Beep Volume” on page 72
Referenced Control Register Location
Limiter Rates .......................
Limiter Thresholds
LIMSRDIS............................
Master Volume Control ........ “Limiter Release Rate” on page 86 , “Limiter Attack Rate” on page 87
“Limiter Maximum Threshold” on page 85 , “Limiter Cushion Threshold” on page 85
“Limiter Soft Ramp Disable” on page 82
“Master Volume Control: MSTA (Address 13h) & MSTB (Address 14h)” on page 70
FREQ[3:0]
...
BPVOL[4:0]
ONTIME[3:0] OFFTIME[2:0]
BEEP[1:0] =
'01'
BEEP[1:0] =
'10'
BEEP[1:0] =
'11'
SINGLE-BEEP: Beep turns on at a
configurable frequency (FREQ) and
volume (BPVOL) for the duration of
ONTIME. BEEP must be cleared
and set for additional beeps.
MULTI-BEEP: Beep turns on at a configurable frequency (FREQ)
and volume (BPVOL) for the duration of ONTIME and turns off for
the duration of OFFTIME. On and off cycles are repeated until
REPEAT is cleared.
CONTINUOUS BEEP: Beep turns on at a configurable frequency (FREQ) and volume (BPVOL) and remains on
until REPEAT is cleared.
Figure 29. Beep Configuration Options