Cirrus Logic CS42L55 - Manual (Page 32)

32 DS773F1
CS42L55
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.
Notes:
1. Recommended settings: Best limiting performance may be realized with the fastest attack and
slowest release setting with soft ramp enabled in the control registers. The CUSH bits allow the user
to set a threshold slightly below the maximum threshold for hysteresis control - this cushions the
sound as the limiter attacks and releases.
2. 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.
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 18h) & MSTB (Address 19h)” on page 57
“PCMx Mixer Volume: PCMA (Address 12h) & PCMB (Address 13h)” on page 52
“Beep Off Time” on page 54
“Beep On Time” on page 54
“Beep Frequency” on page 53
“Beep Configuration” on page 55
“Beep Volume” on page 55
Referenced Control Register Location
Limiter Rates .......................
Limiter Thresholds
LIMSRDIS ...........................
Master Volume Control........ “Limiter Release Rate” on page 62 , “Limiter Attack Rate” on page 62
“Limiter Maximum Threshold” on page 60 , “Limiter Cushion Threshold” on page 61
“Limiter Soft Ramp Disable” on page 66
“Master Volume Control: MSTA (Address 18h) & MSTB (Address 19h)” on page 57
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 18. Beep Configuration Options