CS4239 Datasheet, PDF (67/98 Pages) Cirrus Logic – CrystalClear™ Portable ISA Audio System

CS4239
CrystalClear^TM Portable ISA Audio System
cupy the right word. The last 32 bits contain four
status bits and 28 zeros. This is the only mode
that contains status information.
The second serial format - SPF1, shown in Fig-
ure 7, is called 64-bit mode. This format has 64
SCLKs per frame, with FSYNC high transitions
at the start of the left data word and low transi-
tions at the start of the right data word. Both the
left and right data words are followed by 16 ze-
ros.
The third serial format - SPF2, shown in Fig-
ure 8, is called 32-bit mode. This format has 32
SCLKs per frame and FSYNC is high for the
left channel and low for the right channel. The
absolute time is similar to the other two modes
but SCLK is stopped after the right channel is
finished. SCLK is held stopped until the start of
the next frame (stopped for 32 bit period times).
This mode is useful for DSPs that do not want
the interrupt overhead of the 32 unused bit peri-
ods. As an example, if a DSP serial word length
is 16 bits, then four interrupts will occur in SPF0
and SPF1 modes. In mode SPF2 the DSP will
only be interrupted twice.
The fourth serial format - SPF3, shown in Fig-
ure 9, is called ADC/DAC mode. This format
has 64 SCLKs per frame, with FSYNC high
transitions at the start of the left ADC data word
and low transitions at the start of the right ADC
data word. For serial data in, SDIN, both the left
and right 16-bit DAC data word should be fol-
lowed by zeros. For serial data out, SDOUT,
both the left and right ADC data words are fol-
lowed by 16 bits of the DAC data words. The
DAC data words are tapped off the data stream
right before the data enters the Codec DACs.
Having the ADC and DAC data on the SDOUT
allows external modem DSPs to cancel the local
audio source from the local microphone signal.
CS9236 WAVETABLE SERIAL PORT
A digital interface to the CS9236 Single-Chip
Wavetable Music Synthesizer is provided that al-
lows the CS9236 PCM audio data to be summed
digitally into the output digital mixer. This serial
port is enabled via the WTEN bit located in
Control register C8/X24 or in the Global Con-
figuration byte in the Hardware Configuration
data. The hardware connections to the CS9236
are illustrated in Figure 11.
FSYNC
SCLK
SDIN
SDOUT
...
...
15 14 13 ^... 0
15 14 13 ^... 0
15
DAC 16 Clocks
DAC 16 Clocks
15 14 13 ^... 0 15 14 13 ^... 0 15 14 13 ^... 0 15 14 13 ^... 0 15
ADC 16 Clocks DAC 16 Clocks
Left Data
ADC 16 Clocks DAC 16 Clocks
Right Data
Figure 9. ADC/DAC Mode (SF1,0 = 11)
DS253PP2
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