Video Circuit (Dec Substrate) - Hitachi DV-P250U Service Manual

Functions of each IC
No. IC
1 IC1101 I/F GATE ARRAY
2 IC1601 SH MICOM
3 IC1602 FLASH MEMORY
4 IC1603 TRACK BUFFER
5 IC1201 A/V DECODER
6 IC2203~IC2204 BUFFER RAM
The following is the description of the functions of each IC:
1. I/F GATE ARRAY (IC1101)
It executes signal timing changes between SH MICOM (IC1601), DVD ROM drive I/F (PG1101), and A/V
decoder (IC1201). It operates on 20MHz clock which is an output from SH MICOM.
2. SH MICOM (IC1601)
It transfers data and executes presetting and control of each IC.
Data transfer from DVD ROM drive I/F is done by setting a register of I/F gate array and by intermediary of
I/F gate array.
In addition, it controls audio DAC ((IC1501~IC1504) and video encoder (IC2202), manages track buffer
(IC1603) and flash memory (IC1602), and communicates with FL MICOM (IC1701).
With 20MHz XTAL(X1601) attached it pulses and is used as a system clock.
3. FLASH MEMORY (IC1602)
A 8Mbits flash memory is used. It stores SH MICOM program and its access is controlled by SH MICOM.
4. TRACK BUFFER (IC1603)
A 4Mbit DRAM is used. It stores data read out from disc. Its control is done by SH MICOM, and its data is
read-written via I/F gate array. In addition a part of this buffer is used as the work area of SH MICOM.
5. A/V DECODER (IC1201)
Data input from track buffer via I/F gate array is separated into audio data and video data. MPEG
compressed data are decompressed (decoded) and output as digital video and digital audio (AC-3). SH
MICOM controls it via I/F gate array. System clock, clock of video interface signals, and clock of audio
interface signals operate by inputting 27MHz respectively.
6. BUFFER SDRAM (IC2203~IC2204)
Two 16 Mbits SDRAM are used. A/V decoder controls it and it is used to decompress audio and video
data compressed by MPEG.

Video circuit (DEC substrate)

8bit YC C digital video stream (P) output from A/V decoder are input to video encoder
R B
ADV7172(IC2202). Video encoder is preset in master mode that generates reference signals and
receives 27MHz from system clock X2203 and outputs H,V synchronous signals to A/V decoder.
By presetting of internal register, video encoder generates:
1. NTSC (North America, Japan, Taiwan)
2. PAL (Europe, Asia)
standard analog video signals.
10
Functions
Execute data transfer timings from ATAPI to track buffer,
and from track buffer to A/V decoder.
Execute data transfer, presetting and control of each IC.
Store memory for SH MICOM software
Buffer memory for data transfer
Execute decompression (decoding) of data compressed by
MPEG
Memory used for decompression (decoding) of data
compressed by MPEG and controlled by A/V decoder
Operating
Voltage
5V
5V
5V
5V
3.3V
3.3V
Chapter 1