CS4239 Datasheet, PDF (69/98 Pages) Cirrus Logic – CrystalClear™ Portable ISA Audio System

CS4239
CrystalClear^TM Portable ISA Audio System
Calibration
The WSS Codec has four different calibration
modes. The selected calibration occurs whenever
the Mode Change Enable (MCE, R0) bit goes
form 1 to 0.
The completion of calibration can be determined
by polling the Auto-Calibrate In-Progress bit in
the Error Status and Initialization register (ACI,
I11). This bit will be high while the calibration is
in progress and low once completed. Transfers
enabled during calibration will not begin until
the calibration cycle has completed. Since the
part always operates at 44.1 kHz internally, all
calibration times are based on 44.1 kHz sample
periods.
The Calibration procedure is as follows:
1) Place the WSS Codec in Mode Change
Enable using the MCE bit of the Index Ad-
dress register (R0).
2) Set the CAL1,0 bits in the Interface Configura-
tion register (I9).
3) Return from Mode Change Enable by reset-
ting the MCE bit of the Index Address
register (R0).
4) Wait until 80h NOT returned
5) Wait until ACI (I11) cleared to proceed
NO CALIBRATION (CAL1,0 = 00)
This is the fastest mode since no calibration is
performed. This mode is useful for games which
require the sample frequency be changed
quickly. This mode is also useful when the codec
is operating full-duplex and an ADC data format
change is desired. This is the only calibration
mode that does not affect the DACs (i.e. mute
the DACs). The No Calibration mode takes zero
sample periods.
CONVERTER CALIBRATION (CAL1,0 = 01)
This calibration mode calibrates the ADCs and
the DACs, but does not calibrate any of the ana-
log mixing channels. This is the second longest
calibration mode, taking 321 sample periods at
44.1 kHz. Because the analog mixer is not cali-
brated in this mode, any signals fed through the
mixer will be unaffected. The calibration se-
quence is as follows:
The DACs are muted
The ADCs are calibrated
The DACs are calibrated
The DACs are unmuted
DAC CALIBRATION (CAL1,0 = 10)
This calibration mode only clears the DACs
(playback) interpolation filters leaving the ADC
unaffected. This is the second fastest calibration
mode (no cal. is the fastest) taking 120 sample
periods at 44.1 kHz to complete. The calibration
sequence is as follows:
The DACs are muted
The DAC filters are cleared
The DACs are unmuted
FULL CALIBRATION (CAL1, 0 = 11)
This calibration mode calibrates all offsets,
ADCs, DACs, and analog mixers. Full calibra-
tion will automatically be initiated on power up
or anytime the WSS Codec exits from a full
power down state. This is the longest calibration
mode and takes 450 sample periods at 44.1 kHz
to complete. The calibration sequence is as fol-
lows:
All outputs are muted (DACs and mixer)
The mixer is calibrated
The ADCs are calibrated
The DACs are calibrated
All outputs are unmuted
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