CS4239 Datasheet, PDF (42/98 Pages) Cirrus Logic – CrystalClear™ Portable ISA Audio System

CS4239
CrystalClear^TM Portable ISA Audio System
DIV5 - DIV0
Clock Divider. These bits select the
audio sample frequency for both cap-
ture and playback. These bits can
be overridden by IFSE in X11.
Fs = (2*XT)/(M*N)
XT = 24.576 MHz CS2 = 0
XT = 16.9344 MHz CS2 = 1
N = DIV5-DIV0
16 ≤ N ≤ 49 for XT = 24.576 MHz
12 ≤ N ≤ 33 for XT = 16.9344 MHz
(M set by OSM1,0 in I10)
M = 64 for Fs > 24 kHz
M = 128 for 12 kHz < Fs ≤ 24 kHz
M = 256 for Fs ≤ 12 kHz
SRE
Alternate Sample Rate Enable. When
this bit is set to a one, bits 0-3 of I8
will be ignored, and the sample fre-
quency is then determined by CS2,
DIV5-DIV0, and the oversampling
mode bits OSM1, OSM0 in I10. Note
that this register can be overridden
(disabled) by IFSE in X11.
Extended Register Access (I23)
Default = xxxxxxxx
D7 D6 D5 D4 D3 D2 D1 D0
XA3 XA2 XA1 XA0 XRAE XA4 res rbc
XA4
Extended Register Address bit 4.
Along with XA3-XA0, enables ac-
cess to extended registers X16
through X31. MODE 3 only.
XRAE
Extended Register Access Enable.
Setting this bit converts this register
from the extended address register
to the extended data register. To con-
vert back to an address register, R0
must be written. MODE 3 only.
XA3-XA0
Extended Register Address. Along
with XA4, sets the register number
(X0-X31) accessed when XRAE is
set. MODE 3 only. See the WSS Ex-
tended Register section for more
details.
Alternate Feature Status (I24)
Default = x0000000
D7 D6 D5 D4 D3 D2 D1 D0
res
rbc
CI
PI
CU CO PO PU
PU
Playback Underrun: When set,
indicates the DAC has run out of
data and a sample has been missed.
PO
Playback Overrun: When set,
indicates that the host attempted to
write data into a full FIFO and the
data was discarded.
CO
Capture Overrun: When set,
indicates that the ADC had a sample
to load into the FIFO but the FIFO
was full. In this case, this bit is set
and the new sample is discarded.
CU
Capture Underrun: Indicates the host
has read more data out of the FIFO
than it contained. In this condition,
the bit is set and the last valid byte
is read by the host.
PI
Playback Interrupt: Indicates an
interrupt is pending from the play-
back DMA count registers.
CI
Capture Interrupt: Indicates an
interrupt is pending from the capture
DMA count registers.
The PI and CI bits are reset by writing a "0" to
the particular interrupt bit or by writing any
value to the Status register (R2).
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