Cirrus Logic CS43L21 - Manual (Page 26)

26 DS723F1
CS43L21
4.3.5 Tone Control
Shelving filters are used to implement bass and treble (boost and cut) with four selectable corner frequen-
cies. Boosting will affect peak detect and limiting when levels exceed the maximum threshold settings.
4.3.6 Limiter
When enabled, the limiter monitors the digital input signal before the DAC modulator, detects when levels
exceed the maximum threshold settings and lowers the AOUT volume at a programmable attack rate be-
low the maximum threshold. When the input signal level falls below the maximum threshold, the AOUT
volume returns to its original level set in the Volume Control register at a programmable release rate. At-
tack 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.
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 “cushion” bits allow the user to set a
threshold slightly below the maximum threshold for hysteresis control - this cushions the sound as the lim-
iter attacks and releases.
Note:
1. When the Limiter is enabled, the AOUT Volume is automatically controlled and should not be adjusted
manually. Alternative volume control may be realized using the PCMMIXx_VOL[6:0] bits.
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.
Software
Controls:
“Tone Control (Address 15h)” on page 49 .
Software
Controls: “Limiter Release Rate Register (Address 1Ah)” on page 52 , “Limiter Attack Rate Register (Address
1Bh)” on page 53 , “DAC Control (Address 09h)” on page 43
FREQ[3:0]
...
BPVOL[4:0]
ONTIME[3:0] OFFTIME[2:0]
REPEAT = '0'
BEEP = '1'
REPEAT = '1'
BEEP = '0'
REPEAT = '1'
BEEP = '1'
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 10. Beep Configuration Options