Sharp 32LF-94EC, Service Manual, Page: 44 / 82

20
AK53 D.O.C. Service Manual 22/03/2004
12.9.PNX300X (IC313)
This IC is the heart of the TV set for small signal processing.
12.9.1.General Description of the Digital One Chip System
DOC Hardware
The Digital One Chip System (DOC) is a system concept based on a digital processor for double-scan
TV receivers. It is a global, multi-standard system primarily designed for the reception and processing
of analog broadcast signals. The DOC system serves the TV functionality for small signal processing of
audio, video, VBI services, graphics and control. An integrated MIPS 1910 processor runs the
DOCware software stack. The Digital One Chip DOCware software is stored in a non-volatile external
memory, normally flash memory. The following figure shows the hardware system architecture of a TV
chassis based on the DOC system.
The dual stream architecture of the DOC system allows audio and video processing of two A/V sources
simultaneously. The two video streams can be displayed in several programmable ways (main screen,
PIP or DW). The two audio streams are audible via the TV loudspeakers and/or the headphones. If two
TV broadcast signals have to be processed simultaneously, an external IF processor and a PIP Mono
Sound Demodulator/Decoder is needed.
For the memory-based features in the DOC system (like scan rate conversion, dynamic noise reduction
and PIP/DW applications) external SDRAM is needed. The memory size requirements are directly
related to which memory-based features have to be supported. The amount of SDRAM required varies
per feature but also varies with combination of features.
The DOC system also has 128kByte of internal SRAM memory. This memory is used to run low
latency, timing critical parts of the software. Under these circumstances no external SDRAM is needed.
The DOC system is built around the ADOC IC. This chip implements all TV functions in digital
technology. Only a few functions (like AD-conversion, IF processing and source select) are
implemented in an analog companion IC, the MPIF.
The MPIF is meant as an analog video and audio pre-processing unit for the TV processor ADOC. It
contains the high frequent IF part and all the analog video and audio source switching for external in-
and outputs. MPIF can handle CVBS, Y/C, RGB (1Fh/2Fh) and YPrPb (1Fh/2Fh) video signals as well
as stereo Left/Right and Second Sound IF (low-IF 5-6MHz, 10.7Mhz) audio signals. MPIF converts the
selected video and audio streams from the analog to the digital domain. Via three high-speed serial
data links the digitized audio and video signals are streamed to the ADOC IC for further processing.
ADOC is a fully integrated, digitally implemented TV processor for audio, video, VBI services, graphics
and control.
The split-up between an analog (MPIF) and a digital part (ADOC) has the following advantages:
• High frequency IF part can be included in the concept
• Less A/D and D/A converters needed for source switching
• Better performance for AD converters (realized in analog design environment, more accurate, less
tolerance)
• Critical items like reference voltages can be realized in the analog environment