21
CS7808
rupts can be generated on specific or generic
events. Infrared inputs can be filtered to make them
free of glitches or stored unfiltered into memory.
Control of all the internal clocks is also possible.
Internal PLLs are used to generate the internal sys-
tem and memory clocks and audio clocks of any
widely used frequency.
3.8
The CS7808 has a programmable interface port
which can be configured to connect to industry-
standard ATAPI interfaces without external glue
logic.
Host Interface
The Host interface can be set up in ATAPI mode,
to connect directly to any ATAPI hard-disk drive
(using two chip selects).
3.9
Compressed MPEG data is read from Internet
through Ethernet controller(Host I/F) or soft mo-
dem(CODEC I/F) into an input FIFO in DRAM.
The data flow (DMA) controller moves Video
packets from the input FIFO into the MPEG decod-
er’s input FIFO (also in DRAM). The DMA con-
troller can also perform advanced functions such as
start code search, relieving the RISC processors.
The System Synchronization function is used to
control the timing of MPEG picture decoding. The
MPEGVideo decoderprocesses I, B, and P frames,
and writes to video frame buffers in DRAM for
output to the display. Special anti-tearing logic en-
sures that currently displayed frame buffers are not
overwritten.
MPEG Video Decoding
3.10
Compressed Audio data is decompressed, then
written to a PCM output FIFO, also in DRAM The
DMA and decompression stages of audio process-
ing can be done with a combination of the DMA
unit, DSP, and RISC processors. The DSP is opti-
mized for audio processing, so most common for-
mats can be handled by the DSP alone, including
AC-3,DTS, MPEG2audio, and MP3. TheDSP has
Audio Processing
enough reserve bandwidth to handle the Karaoke
echo-mix and pitch shift, and AC-3 down-mix
functions.
The audio output data is written into a DRAM
FIFOin 16-, 18-, 20-or24-bit PCM format. Aflex-
ible audio output stage can simultaneously output 8
channels of PCM data to audio DACs, or 6 chan-
nels of audio data plus an IEC-958 encoded output,
at up to 96 KHz. The audio interface also includes
a flexible PCM input interface, which can input a
wide range of protocols from an audio ADC or an
IEC-958 receiver.
3.11
The soft modem processing is handled by one of
the RISC processors, which is typically dedicated
for that function. Data rates up to 56 Kbits (V.90
protocol) are supported. The CS7808 interfaces to
a simple external CODEC/DAA circuit using a
flexibleserialinterface.Theserialinterfaceisaful-
ly programmable, bi-directional interface and can
be used either as aPCM interface oras an AC97 in-
terface. In PCM mode, the sample size could be ad-
justed to 20, 18 or 16 bits to match common DAC
and ADC formats, or any other specific size. In
AC97 mode, any slot can be used to interfaceeither
a modem CODEC or an audio CODEC.
Soft Modem
3.12
The Digital Video Interface provides flexible and
powerful means of outputting digital video data to
external devices in CCIR601/3 and CCIR656 for-
mats. The interface directly supports NTSC/PAL
video encoding, in both master and slave synchro-
nization configurations. The internal frame buffer
format could be 4:2:0, 4:2:2, YUV655, RGB565
and RGB555. Cirrus Logic provides some easy-to-
use utilities in order to get the best advantage of the
powerfulvideofilteringcapabilitiesoftheCS7808.
The CS7808 also features an NTSC/PAL video de-
coder input interface. The interface accepts
CCIR601, CIF, and QCIF formats, out of many TV
decoders on the market. The video processor also
Video