SAA7201H Philips Semiconductors, SAA7201H Datasheet - Page 11

• Manufacturer Part Number: SAA7201H
• Description: Integrated MPEG2 AVG decoder
• Manufacturer: Philips Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
General
The SAA7201 is an MPEG2 decoder which combines
audio decoding, video decoding and enhanced region
based graphics. The decoder operates with a single
16 Mbit external synchronous dynamic random access
memory (SDRAM) and runs from a single external 27 MHz
clock. Due to the optimized memory control for MPEG2
decoding, more than 1 Mbit is available for graphics in
50 Hz systems.
MPEG2 data can be accepted up to 9 Mbytes/s through a
dedicated byte wide interface. The data on this interface
can be either in PES (Packetized Elementary Stream),
MPEG1 packet or ES (Elementary Stream) format as
described in Chapter “References”. Two additional strobe
signals distinguish between audio and video data.
The internal video decoder is capable of decoding all
MPEG compliant streams up to main level main profile as
specified in Chapter “References”. The audio decoder
implements 2 channel audio decoding according to the
standards in Chapter “References”.
All real time audio/video decoding and synchronization
tasks are performed autonomously, so the external
microcontroller only needs to perform high-level tasks like
initialization, status monitoring and trick mode control.
The main support task of the external microcontroller
concerns the control of the graphical unit. This unit should
1997 Jan 29
handbook, full pagewidth
Integrated MPEG2 AVG decoder
V_STROBE
A_STROBE
AV_DATA
ERROR
(0 to 7)
Fig.3 Timing diagram of parallel input mode.
25 ns
video byte (n)
111 ns
25 ns
11
be supplied with bit-maps, determining the contents of the
graphical regions and by a simple set of instructions
determining the appearance of the graphical data on the
screen. Most graphical information should be stored in the
external memory which implies multiple data transfers
between CPU and the external memory. By performing
these data transfers on a direct memory access (DMA)
basis, full bit-maps can be transferred within one video
frame period.
The video output, containing a mix of MPEG video and
graphical data, is at a YUV multiplexed format which can
be directly connected to an external composite video
encoder. The audio output, containing a mix of MPEG
audio and programmable ‘beeps’, is in a serial, I
Japanese format which can be directly supplied to most
commercially available up-sampling audio DA converters.
A functional block diagram of the decoder is given in Fig.1.
Its application environment is depicted in Fig.24. In the
following sections, a brief description of the individual
internal blocks of the MPEG2 decoder will be given.
Audio/video interface
In a basic set-top box application the SAA7201 receives
audio and video PES data in a byte wide format at rates up
to 9 Mbytes/s. A timing diagram is shown in Fig.3. Next to
the 8-bit wide data bus an audio and video strobe is
expected at the input. Erroneous data may be flagged via
the error indicator.
video byte (n + 1)
Objective specification
audio byte (m)
SAA7201
MGD323
2
S or