CS4237B Datasheet, PDF (26/114 Pages) Cirrus Logic – CrystalClear Advanced Audio System with 3D Sound

CS4237B
specific E²PROM data sheet to select the value
of the pull-up resistor (a typical value would be
3.3kΩ).
Programming the E²PROM:
1. Configure Control I/O base address by one
of two methods: regular PnP cycle or Crystal
Key method.
a. The host can use the regular PnP cycle to
program the logical device 2 I/O base ad-
dress, and then place the chip in the
wait_for_key_state
b. If the Crystal Key method is used:
First, write to I/O 0279h, send the 32-
byte Crystal key. (The Crystal Key only
supports one Crystal part per system.)
Second, configure the Control I/O base
address by writing 15h, 02h, 47h, 01h,
20h, 33h, 01h, 79h to 0279h.
2. Refer to the specific data sheet for the
E²PROM you are using for timing require-
ments and data format. Also, refer to the
Loading Resource Data section of this data
sheet for the E²PROM resource data format.
3. Send the E²PROM data in successive bits to
CTRLbase+1 (Hardware Control Register)
while following the E²PROM data sheet for-
mat.
The E²PROM now contains the PnP resource
data. For this new data to take effect, the part
must be reset, causing the part to read the
E²PROM during initialization. Crystal can pro-
vide a utility, RESOURCE.EXE, to program
E²PROMs through the Control logical device in-
terface.
26
WINDOWS SOUND SYSTEM CODEC
The WSS Codec software interface consists of 4
I/O locations starting at the Plug and Play ad-
dress ’WSSbase’, and supports 12-bit address
decoding. If the upper address bits, SA12-SA15
are used, they must be 0 to decode a valid ad-
dress. The WSS Codec also requires one
interrupt and one or preferably two DMA chan-
nels, one for playback and one for capture. Since
the WSS Codec and Sound Blaster device are
mutually exclusive, the two devices share the
same interrupt and DMA playback channel.
The WSS Codec/Mixer is register compatible
with the Microsoft Windows Sound System.
Functions include stereo Analog-to-Digital and
Digital-to-Analog converters (ADCs and DACs),
analog mixing, anti-aliasing and reconstruction
filters, line and microphone level inputs, optional
A-Law/µ-Law coding, simultaneous capture and
playback (at independent sample frequencies)
and a parallel bus interface. Five analog inputs
are provided and four can be mixed to the ADC
mixer. All five can be mixed with the output of
the DAC with full volume control. Several data
modes are supported including 8- and 16-bit lin-
ear as well as 8-bit companded, 4-bit ADPCM
compressed, and 16-bit big Endian.
Enhanced Functions (MODEs)
The initial state is labeled MODE 1 and forces
the part to appear as a CS4248. The more popu-
lar second mode, MODE 2, forces the part to
appear as a CS4231 super set and is compatible
with the CS4232. To switch from MODE 1 to
MODE 2, the CMS1,0 bits, in the MODE and
ID register (I12), should be set to 10 respec-
tively. When MODE 2 is selected, the bit IA4 in
the Index Address register (R0) will be decoded
as a valid index pointer providing 16 additional
registers and increased functionality over the
CS4248.
To reverse the procedure, set the CMS1,0 bits to
00 and the part will resume operation in
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