AT83C51SND1C_03 ATMEL [ATMEL Corporation], AT83C51SND1C_03 Datasheet - Page 74

• Manufacturer Part Number: AT83C51SND1C_03
• Description: Single-Chip Flash Microcontroller with MP3 Decoder and Human Interface
• Manufacturer: ATMEL [ATMEL Corporation]

Clock Generator
Data Converter
74
AT8xC51SND1C
The audio interface clock is generated by division of the PLL clock. The division factor is
given by AUCD4:0 bits in CLKAUD register. Figure 49 shows the audio interface clock
generator and its calculation formula. The audio interface clock frequency depends on
the incoming MP3 frames and the audio DAC used.
Figure 49. Audio Clock Generator and Symbol
As soon as audio interface is enabled by setting AUDEN bit in AUDCON1 register, the
master clock generated by the PLL is output on the SCLK pin which is the DAC system
clock. This clock is output at 256 or 384 times the sampling frequency depending on the
DAC capabilities. HLR bit in AUDCON0 register must be set according to this rate for
properly generating the audio bit clock on the DCLK pin and the word selection clock on
the DSEL pin. These clocks are not generated when no data is available at the data
converter input.
For DAC compatibility, the bit clock frequency is programmable for outputting 16 bits or
32 bits per channel using the DSIZ bit in AUDCON0 register (see Section "Data Con-
verter", page 74), and the word selection signal is programmable for outputting left
channel on low or high level according to POL bit in AUDCON0 register as shown in
Figure 50.
Figure 50. DSEL Output Polarity
The data converter block converts the audio stream input from the 16-bit parallel format
to a serial format. For accepting all PCM formats and I
AUDCON0 register are used to shift the data output point. As shown in Figure 51, these
bits allow MSB justification by setting JUST4:0 = 00000, LSB justification by setting
JUST4:0 = 10000, I
LSB justification by filling the low significant bits with logic 0.
CLOCK
PLL
POL = 0
POL = 1
2
AUCD4:0
AUDCLK
S Justification by setting JUST4:0 = 00001, and more than 16-bit
AUDclk
Left Channel
Left Channel
Audio Interface Clock
=
---------------------------
AUCD
PLLclk
+
1
Right Channel
Right Channel
2
S format, JUST4:0 bits in
Audio Clock Symbol
CLOCK
AUD
4109E–8051–06/03