Rainbow Electronics AT89C51SND1C - Manual (Page 77)

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AT8xC51SND1C
4109E–8051–06/03
Figure 53. MP3 Mode Audio Configuration Flow
Voice or Sound Playing In voice or sound playing mode, the operations required are to configure the PLL and
the audio interface according to the DAC selected. The audio clock is programmed to
generate the 256·Fs or 384·Fs as for the MP3 playing mode. The data flow sent by the
C51 is then regulated by interrupt and data is loaded 4 Bytes by 4 Bytes. Figure 54
shows the configuration flow of the audio interface when in voice or sound mode.
Figure 54. Voice or Sound Mode Audio Flows
Note: 1. An under-run occurrence signifies that C51 core did not respond to the previous sample request interrupt. It may never
occur for a correct voice/sound generation. It is the user’s responsibility to mask it or not.
MP3 Mode
Configuration
Configure Interface
HLR = X
DSIZ = X
POL = X
JUST4:0 = XXXXXb
SRC = 0
Program Audio Clock
Enable DAC System
Clock
AUDEN = 1
Wait For
DAC Set-up Time
Enable Data Request
DRQEN = 1
Select Audio
SRC = 1
Voice/Song Mode
Configuration
Configure Interface
HLR = X
DSIZ = X
POL = X
JUST4:0 = XXXXXb
DUP1:0 = XX
Program Audio Clock
Enable DAC System
Clock
AUDEN = 1
Wait for DAC
Enable Time
Load 8 Samples in the
Audio Buffer
Enable Interrupt
Set MSREQ & MUDRN 1
EAUD = 1
Audio Interrupt
Service Routine
Under-run Condition 1 Load 4 Samples in the
Audio Buffer
Sample Request?
SREQ = 1?