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2.12 Stereo Codec
A 16-bit audio quality stereo codec, Crystal Semiconductor CS4218, is connected to the
DSP56852's ISSI port to support audio, voice and signal analysis applications. The codec
is clocked with a 12.288MHz oscillator. This allows the codec to operate between a
sample frequency of 8KHz and 48KHz. The sample rate can be manually set by setting the
appropriate switch positions on DIP switch S4. The sample rate selections possible using
this three-position DIP switch are detailed in
levels, eliminating the need for voltage level translation circuitry. Additionally, a set of
zero ohm resistors are provided on the EVM to allow a user to disconnect the on-board
codec from the ISSI port and allow him to connect his own codec to the ISSI port; see
Figure
2-12. The on-board codec has analog signal conditioning logic, allowing direct
connection to its line level input and line level output signals through two 1/8" stereo
jacks; reference
Figure
Position 3
2.12.1 Analog Input/Output
The DSP56852EVM uses jacks for line-level stereo input, line-level stereo output and
stereo headphone output. A National Semiconductor LM4880 provides the drive required
for the use of headphones. This device offers a THD, which is superior by a factor of two
to the CS4218's on-chip headphone drive circuitry. The basic Analog codec connections
are shown in
Figure
MOTOROLA
Freescale Semiconductor, Inc.
2-11.
Table 2-8. Codec Sample Rate Selector
SW 4
SW 4
Position 2
Position 3
(MF6)
(MF7)
ON
ON
ON
ON
ON
OFF
ON
OFF
OFF
ON
OFF
ON
OFF
OFF
OFF
OFF
2-11.
Technical Summary
For More Information On This Product,
Go to: www.freescale.com
Table
2-8. The codec supports +3.3V digital
SW 4
Sample Rate
(MF8)
ON
48.00KHz
OFF
32.00KHz
ON
24.00KHz
OFF
19.20KHz
ON
16.00KHz
OFF
12.00KHz
ON
9.60KHz
OFF
8.00KHz
Stereo Codec
2-15
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