Cirrus Logic CS43L22 - Manual (Page 22)

22 DS792F2
CS43L22
Confidential Draft
3/4/10
4.2.1 Beep Generator
The Beep Generator generates audio frequencies across approximately two octave major scales. It offers
three modes of operation: Continuous, multiple and single (one-shot) beeps. Sixteen on and eight off
times are available.
Note: The Beep is generated before the limiter and may affect desired limiting performance. If the lim-
iter function is used, it may be required to set the beep volume sufficiently below the threshold to prevent
the peak detect from triggering. Since the master volume control, MSTxVOL[7:0], will affect the beep vol-
ume, DAC volume may alternatively be controlled using the PCMxVOL[6:0] bits.
4.2.2 Limiter
When enabled, the limiter monitors the digital input signal before the DAC and PWM 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/zero cross settings and sample
rate, Fs. Limiter soft ramp and zero cross dependency may be independently enabled/disabled.
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 MIN 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
Referenced Control Register Location
MSTxVOL[7:0].....................
PCMxVOL[6:0] ....................
OFFTIME[2:0] .....................
ONTIME[3:0] .......................
FREQ[3:0] ...........................
BEEP[1:0]............................
BEEPMIXDIS ......................
BPVOL[4:0] ......................... “Master Volume Control: MSTA (Address 20h) & MSTB (Address 21h)” on page 51
“PCMx Volume: PCMA (Address 1Ah) & PCMB (Address 1Bh)” on page 47
“Beep Off Time” on page 48
“Beep On Time” on page 48
“Beep Frequency” on page 47
“Beep Configuration” on page 49
“Beep Mix Disable” on page 49
“Beep Volume” on page 49
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
BEEP is cleared.
CONTINUOUS BEEP: Beep turns on at a configurable frequency (FREQ) and volume (BPVOL) and remains on
until BEEP is cleared.
Figure 6. Beep Configuration Options