CS4235 Datasheet, PDF (67/94 Pages) Cirrus Logic – CrystalClear Low Cost ISA Audio System

CS4235
CrystalClear ^TM Low Cost ISA Audio System
100 Ω
MCLK
LRCLK
SDATA
BRESET
MIDOUT
MIDIN
100k Ω
100k Ω
CS9236
MCLK5I
LRCLK
SOUT
RST
PDN
MIDI_IN
XTAL3I
Midi In
Midi Out
Joystick Connector
Figure 10. CS9236 Wavetable Serial Port Interface
The CS9236 data is sent to DAC2 which can be
summed into the input or output mixer. Volume
control for the serial port is supported through
I18 and I19 in the WSS register space.
WSS CODEC SOFTWARE DESCRIPTION
The WSS Codec must be in Mode Change En-
able Mode (MCE=1) before any changes to the
Interface Configuration register (I9) or the Sam-
ple Frequency (lower four bits) in the Fs &
Playback Data Format registers (I8) are allowed.
The actual audio data formats, which are the up-
per four bits of I8 for playback and I28 for
capture, can be changed by setting MCE (R0) or
PMCE/CMCE (I16) high. The exceptions are
CEN and PEN which can be changed "on-the-
fly" via programmed I/O writes. All outstanding
DMA transfers must be completed before new
values of CEN or PEN are recognized.
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.
DS252PP2
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-
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