USB Audio Design Guide
L8A-64-TQ128
Codec
CS427
0
11.2896 MHz
Crystal
24.576 MHz
Crystal
MCLK
BCLK
LRCLK
SDIN
SDOUT
MCLK_SEL
Figure 35:
Audio Clock
Connections
CODEC mode
CODEC sample rate range (kHz)
Single-Speed
4-54
Double-Speed
50-108
Quad-Speed
100-216
Figure 36:
CODEC
Modes
The internal master clock dividers are set using the MDIV pins. MDIV is tied low
and MDIV2 is connected to bit 2 of port 32A (as well as to the master clock select).
With MDIV2 low, the master clock must be 256Fs in single-speed mode, 128Fs in
double-speed mode and 64Fs in quad-speed mode. This allows an 11.2896MHz
master clock to be used for sample rates of 44.1, 88.2 and 176.4kHz.
With MDIV2 high, the master clock must be 512Fs in single-speed mode, 256Fs
in double-speed mode and 128Fs in quad-speed mode. This allows a 24.576MHz
master clock to be used for sample rates of 48, 96 and 192kHz.
When changing sample frequency, the
CodecConfig()
function first puts the CODEC
into reset by setting
P32A[1]
low. It selects the required master clock/CODEC
dividers and keeps the CODEC in reset for 1ms to allow the clocks to stabilize. The
CODEC is brought out of reset by setting
P32A[1]
back high.
6.1.3
HID
The
reference
design
implements
basic
HID
controls.
The
call
to
vendor_ReadHidButtons()
simply reads from buttons A and B and returns their
state in the relevant bits depending on the desired functionality (play/pause/skip
etc). Note the buttons are active low, the HID controls active high. The buttons are
therefore read and then inverted.
XM0088546.1
Содержание xCORE-200 Multi-channel Audio board
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